Geotechnical mechanics characterization method and controller based on particle flow discrete element numerical simulation

Abstract

The present application is applicable to the field of geotechnical engineering, and provides a geotechnical mechanics characterization method and controller based on particle flow discrete element numerical simulation, the method comprising: using a triaxial compression test of geotechnical materials indoors, obtaining and analyzing the compressive stress-strain curve of the geotechnical materials under different confining pressures on a macroscopic scale, determining the nonlinear dynamic mapping relationship between the elastic modulus of the geotechnical materials and the change of the spherical stress, and establishing a three-dimensional particle flow discrete element numerical model on a microscopic scale based on the nonlinear dynamic mapping relationship; conducting secondary development of the numerical model based on the PB contact model, obtaining a VSPB contact model that actively changes rigidity according to the stress environment, optimizing the values ​​of the contact parameters based on the VSPB contact model, and determining the final compressive stress-strain curve of the geotechnical materials using triaxial numerical tests. The present application can solve the problem of significant imprecision and uncertainty in the technical path when the parameters calibrated based on the uniaxial compression test are directly applied to the triaxial compression numerical simulation.

Description

Technical Field

[0001] The present application belongs to the field of geotechnical mechanics engineering, and in particular, relates to a geotechnical mechanics characterization method and controller based on particle flow discrete element numerical simulation. Background Art

[0002] Geotechnical porous materials are typical confining pressure-sensitive materials, and their mechanical responses under different confining pressures are different. When a triaxial compression test is carried out on a complete geotechnical specimen of standard size under a specific confining pressure, the stress-strain curve of the geotechnical material shows an "S"-shaped nonlinear distribution before reaching the peak strength. As the confining pressure increases, the elastic modulus and peak strength also increase, and the failure mode gradually changes from brittle failure to ductile failure, showing obvious pressure-sensitive characteristics.

[0003] It is a common method to simulate the mechanical response of rock and soil by using the particle flow program PFC3D particle discrete element. This technology is based on the discrete medium theory. By setting the bonding contact model between particles, it can study the influence of microscopic bonding on the macroscopic mechanical properties of granular materials. However, the discrete element method has uncertainty and multiple solutions. First, in the calibration of discrete element model parameters, the contact stiffness of particles is usually preset as a constant and will not change during loading. Second, the reliability of the simulation results of the three-dimensional specimens is low when a simplified two-dimensional discrete element model is used to simulate the test results. Third, due to the dense extrusion and stable contact of the simulated specimens, the nonlinear evolution characteristics of the pre-peak stress-strain curve cannot be reflected. Fourth, when the discrete element parameters calibrated by the uniaxial compression numerical test are directly applied to the triaxial compression numerical simulation, large deviations often occur.

[0004] Therefore, when the discrete element method is used to predict the response of geotechnical mechanics, its model parameters are fixed and the model dimensions are simplified, so that when the parameters calibrated based on the uniaxial compression test are directly applied to the triaxial compression numerical simulation, the technical path has significant imprecision and uncertainty. Summary of the invention

[0005] In order to overcome the problems existing in the related technology, the embodiment of the present application provides a geotechnical mechanics characterization method and controller based on particle flow discrete element numerical simulation, which can solve the problem that when the parameters calibrated based on uniaxial compression test are directly applied to triaxial compression numerical simulation, the technical path has significant imprecision and uncertainty.

[0006] This application is implemented through the following technical solutions:

[0007] In a first aspect, the present application provides a geotechnical mechanics characterization method based on particle flow discrete element numerical simulation, including:

[0008] Using triaxial compression test of rock and soil indoors, the compressive stress-strain curve of rock and soil under different confining pressures on a macro scale is obtained;

[0009] Analyze the compressive stress-strain curves of rock and soil under different confining pressures, and determine the nonlinear dynamic mapping relationship between the elastic modulus of rock and soil and the change of spherical stress;

[0010] Based on the nonlinear dynamic mapping relationship between the elastic modulus of rock and soil and the spherical stress, a three-dimensional particle flow discrete element numerical model at the microscopic scale is established;

[0011] Based on the linear parallel bond model (PB contact model), the three-dimensional particle flow discrete element numerical model is secondary developed to obtain the actively variable stiffness linear parallel bond model (VSPB contact model) that actively changes stiffness according to the stress environment.

[0012] Taking the macroscopic mechanical parameters of rock and soil as the target, adjusting the contact parameters of the VSPB contact model, and determining the optimized VSPB contact model based on the contact parameters of the VSPB contact model;

[0013] Based on the optimized VSPB contact model, the ultimate compressive stress-strain curve of the rock and soil is determined by triaxial numerical tests.

[0014] In a possible implementation of the first aspect, analyzing the compressive stress-strain curve of rock and soil under different confining pressures to determine the nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil and the change of the spherical stress includes:

[0015] Analyze the stress-strain curve under a single confining pressure and determine the deformation characteristics of multiple deformation stages in the full compression process under a single confining pressure; the multiple deformation stages include compaction stage, elastic deformation stage, pre-peak plastic deformation stage, post-peak plastic deformation stage and residual strength stage; the compaction stage and the elastic deformation stage show nonlinear deformation characteristics;

[0016] Analyze the stress-strain curves under different confining pressures to determine the deformation characteristics of rock and soil under different confining pressures;

[0017] Based on the nonlinear deformation characteristics of the compaction stage and the elastic deformation stage in the full compression process under a single confining pressure and the deformation characteristics of rock and soil under different confining pressures, the nonlinear dynamic mapping relationship between the elastic modulus of rock and soil in the compaction stage and the elastic deformation stage and the change of spherical stress under different confining pressures is determined.

[0018] In a possible implementation of the first aspect, the nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil in the compaction stage and the elastic deformation stage under different confining pressures and the change of the spherical stress is an exponential correlation relationship.

[0019] In a possible implementation of the first aspect, the elastic modulus of the rock and soil in the compaction stage and the elastic deformation stage under different confining pressures E The nonlinear dynamic mapping relationship with the change of spherical stress is expressed as:

[0020]

[0021] in, is the maximum value of elastic modulus; Represents the magnitude of change in elastic modulus; Represents the hardening rate; spherical stress includes stress in the vertical direction and horizontal stress .

[0022] In a possible implementation of the first aspect, based on the nonlinear dynamic mapping relationship between the rock and soil elastic modulus and the spherical stress, a three-dimensional particle flow discrete element numerical model at a microscopic scale is established, including:

[0023] Based on the nonlinear dynamic mapping relationship between the elastic modulus of rock and soil and the change of spherical stress, the PFC3D software was used to select spherical particles within a preset radius, ignoring the delicate microscopic crystal structure inside the rock and soil, and a three-dimensional particle flow discrete element numerical model on a microscopic scale was established.

[0024] In a possible implementation of the first aspect, a three-dimensional particle flow discrete element numerical model is secondary developed based on the PB contact model to obtain a VSPB contact model that actively changes stiffness according to the stress environment, including:

[0025] In the PB contact model, the linear spring and the cemented spring are set to act independently, and the contact parameters are defined; the contact parameters include the linear spring stiffness, the cemented spring stiffness and the friction coefficient of the particles; different contact parameter values ​​correspond to different properties of rock and soil;

[0026] In the three-dimensional particle flow discrete element numerical model, the VSPB contact model that actively changes stiffness according to the stress environment is determined based on the linear spring stiffness and the bond spring stiffness; the VSPB contact model includes the functional relationship between the real-time spring stiffness and the contact stress of the rock and soil in the compaction stage and the elastic deformation stage under different confining pressures; the VSPB contact model is used to traverse the contact status of all particles and update the contact stiffness of the particles based on the contact status of the particles.

[0027] In a possible implementation of the first aspect, the real-time spring stiffness of the rock and soil in the compaction stage and the elastic deformation stage under different confining pressures is Contact stress The functional relationship is expressed as:

[0028]

[0029] in, is the initial value of the normal stiffness of the bonded spring; is the maximum value of the normal stiffness of the bonded spring; To define the hardening coefficient.

[0030] In a possible implementation manner of the first aspect, the contact states of all particles include a first contact state, a second contact state, and a third contact state;

[0031] The first contact state is that the bonding is not destroyed and the contact stress of the particles is greater than 0;

[0032] The second contact state is cementation failure, the contact stress of the particles is greater than 0, and the contact stress of the particles does not decay;

[0033] The third contact state is bonding failure, the contact stress of the particles is greater than 0, and the contact stress of the particles decays to a first preset multiple of the last contact stress of the particles.

[0034] In a possible implementation of the first aspect, updating the contact stiffness of the particles based on the contact state of the particles includes:

[0035] When the contact state of the particles is the first contact state, the bonding spring stiffness and the linear spring stiffness are updated;

[0036] When the contact state of the particles is the second contact state, the linear spring stiffness remains constant;

[0037] When the contact state of the particles is the third contact state, the post-peak linear spring stiffness is attenuated by multiplying the linear spring stiffness by a second preset multiple.

[0038] In a second aspect, the present application provides a controller for executing the geotechnical mechanics characterization method based on particle flow discrete element numerical simulation as in the first aspect.

[0039] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0040] In the embodiment of the present application, the compressive stress-strain curve of rock and soil under different confining pressures on a macro scale is obtained through indoor triaxial compression tests on rock and soil, which ensures the authenticity and reliability of the test data and provides a solid foundation for subsequent analysis. The compressive stress-strain curve of rock and soil under different confining pressures is analyzed to determine the nonlinear dynamic mapping relationship between the elastic modulus of rock and soil and the change of spherical stress, which reveals the mechanical properties of rock and soil under multi-dimensional stress states and provides a theoretical basis for establishing numerical models on a micro scale. Based on the above nonlinear dynamic mapping relationship, a three-dimensional particle flow discrete element numerical model on a micro scale is established, which can reproduce the pre-peak nonlinear deformation mechanical behavior of rock and soil under specific confining pressures, and at the same time reproduce the pressure-sensitive characteristics of rock and soil, converting the test results on a macro scale into a numerical model on a micro scale, realizing the leap from macro to micro. Based on the PB contact model, the three-dimensional particle flow discrete element numerical model was secondary developed, and the VSPB contact model that can update the discrete element contact parameters in real time during the loading process was constructed. The contact parameters of the VSPB contact model were adjusted with the macroscopic mechanical parameters of the rock and soil as the target, and finally the discrete element parameters that can reflect the mechanical properties of the rock and soil can be obtained, which improves the accuracy and applicability of the numerical model. Through a series of rigorous and scientific steps, the problems existing when the parameters calibrated based on the uniaxial compression test are directly applied to the triaxial compression numerical simulation are effectively solved, providing strong support for the in-depth research and practical application of rock and soil mechanics.

[0041] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 It is a flow chart of a geotechnical mechanics characterization method based on particle flow discrete element numerical simulation provided by an embodiment of the present application;

[0044] Figure 2 It is a schematic diagram of the stress-strain curve of the whole compression process of rock and soil under different indoor confining pressures provided by an embodiment of the present application;

[0045] Figure 3 It is a schematic diagram of a stress-strain curve obtained by carrying out a geotechnical triaxial numerical test using an optimized VSPB contact model and specified contact parameters provided in an embodiment of the present application;

[0046] Figure 4is a schematic diagram of the relationship between the elastic modulus and the ball stress provided by an embodiment of the present application;

[0047] Figure 5 is a schematic diagram of a PFC3D triaxial compression sample particle provided in an embodiment of the present application;

[0048] Figure 6 is a schematic diagram of a contact model of a PB contact model provided in an embodiment of the present application; wherein, Figure 6 (a) is a schematic diagram of the structure of two particles cemented together. Figure 6 (b) is a schematic diagram of the cemented contact of the PB contact model; Figure 6 (c) is a schematic diagram of the PB contact model without bonding;

[0049] Figure 7 It is a structural schematic diagram of a geotechnical mechanics characterization device based on particle flow discrete element numerical simulation provided by an embodiment of the present application;

[0050] Figure 8 It is a schematic diagram of the structure of a controller provided in one embodiment of the present application. DETAILED DESCRIPTION

[0051] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0052] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0053] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0054] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0055] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0056] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0057] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0058] Figure 1 is a flow chart of a geotechnical mechanics characterization method based on particle flow discrete element numerical simulation provided by an embodiment of the present application, with reference to Figure 1 , the geotechnical mechanics characterization method based on particle flow discrete element numerical simulation is described as follows:

[0059] The present application provides a geotechnical mechanics characterization method based on particle flow discrete element numerical simulation, including:

[0060] Step 101, using a triaxial compression test of rock and soil indoors, obtain the compressive stress-strain curve of the rock and soil under different confining pressures on a macro scale.

[0061] For example, triaxial compression test of rock and soil is used to obtain the stress-strain curve of the whole compression process of rock and soil under different confining pressures on a macro scale, so as to understand the mechanical properties and deformation characteristics of rock and soil, such as Figure 2 As shown. Figure 2 The horizontal axis is the axial strain , the vertical axis is , is the stress in the vertical direction, is the stress in the horizontal direction.

[0062] Step 102, analyzing the compressive stress-strain curves of the rock and soil under different confining pressures, and determining the nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil and the change of the spherical stress.

[0063] For example, in the initial stage of the stress-strain curve, the geotechnical specimen exhibits compaction and elastic deformation behavior, that is, the stress and strain are nonlinear. This stage is usually used to determine the elastic modulus of the geotechnical specimen. As the stress increases, the geotechnical specimen begins to enter the plastic deformation stage. In this stage, the deformation of the geotechnical specimen is no longer completely reversible, and part of the deformation will be permanently retained. When the stress reaches a certain critical value, the geotechnical specimen will be destroyed and the stress-strain curve will drop sharply.

[0064] Among them, the elastic modulus of rock and soil can be determined by calculating the ratio between stress and strain in the compaction stage and the elastic deformation stage. The elastic modulus is an important parameter that reflects the ability of rock and soil materials to resist elastic deformation. The spherical stress is the average value of the sum of the three principal stresses on the rock and soil specimen. In the triaxial compression test of rock and soil, the spherical stress on the rock and soil specimen can be changed by changing the confining pressure and axial pressure. In order to analyze the influence of spherical stress on the elastic modulus, the elastic modulus under different confining pressures can be associated with the corresponding spherical stress. This correlation is generally nonlinear because the mechanical properties of rock and soil are often affected by many factors, such as particle size, shape, arrangement, and porosity.

[0065] Step 103, based on the nonlinear dynamic mapping relationship between the rock and soil elastic modulus and the spherical stress, a three-dimensional particle flow discrete element numerical model at a microscopic scale is established.

[0066] Based on the above nonlinear dynamic mapping relationship, a three-dimensional particle flow discrete element numerical model at the micro scale is established, which can reproduce the nonlinear deformation mechanical behavior of rock and soil in the compaction stage and elastic deformation stage under specific confining pressure, and at the same time reproduce the pressure-sensitive characteristics of rock and soil, and transform the experimental results at the macro scale into a numerical model at the micro scale, realizing the leap from macro to micro.

[0067] Step 104, secondary development of the three-dimensional particle flow discrete element numerical model is performed based on the PB contact model to obtain a VSPB contact model that actively changes stiffness according to the stress environment.

[0068] Step 105, adjusting the contact parameters of the VSPB contact model with the macroscopic mechanical parameters of the rock and soil as the target, and determining the optimized VSPB contact model based on the contact parameters of the VSPB contact model.

[0069] Step 106, based on the optimized VSPB contact model, the final compressive stress-strain curve of the rock and soil is determined by triaxial numerical test.

[0070] For example, the stress-strain curves obtained by triaxial numerical tests of geotechnical materials using the optimized VSPB contact model and specified contact parameters are as follows: Figure 3 As shown. Under such a calibration method, the triaxial compression test response of rock and soil under a specific confining pressure can be divided into three stages: 1) Nonlinear deformation stage: no damage occurs at this time, and the two spring stiffnesses increase nonlinearly and synchronously, corresponding to the compaction and elastic deformation stage at the macro level; 2) Crack development stage: at this time, partial bonding failure occurs. Since the linear spring stiffness bears the force, the redistribution of the damaged bonding force will not be very obvious, but the overall stiffness is reduced, and it is ductile on the curve, corresponding to the pre-peak plastic deformation stage and post-peak plastic deformation stage at the macro level. 3) Crack penetration failure: microcracks develop to a certain extent until they penetrate, and the specimen fails as a whole. The response under different confining pressures will have the following characteristics: 1) Pre-peak stage: the elastic modulus under high confining pressure is higher than that under low confining pressure. 2) Post-peak stage: low confining pressure presents brittle failure, and gradually transitions to ductile failure as the confining pressure increases.

[0071] For example, after determining the final compressive stress-strain curve of rock and soil, the discrete fracture network (DFN) model can also be introduced to predict the deformation and failure characteristics of the jointed rock mass under triaxial compression, and obtain its physical and mechanical parameters, which greatly improves the accuracy of the discrete element method in reproducing the macroscopic mechanical properties of rock and soil.

[0072] Considering that when the parameters calibrated based on the uniaxial compression test are directly applied to the triaxial compression numerical simulation, the technical path has significant imprecision and uncertainty. At the same time, considering that the traditional particle flow discrete element method cannot reflect the nonlinear deformation and pressure-sensitivity characteristics of porous materials such as rock and soil under different confining pressure conditions, and the stress-strain curve obtained by the numerical experiment cannot match the specimen test, the rock and soil mechanics characterization method based on particle flow discrete element numerical simulation in this embodiment can reproduce the pre-peak nonlinear deformation mechanical behavior of rock and soil under specific confining pressure, and can reproduce the pressure-sensitive characteristics of rock and soil; by comparing with the indoor triaxial test results, the correctness and superiority of this method in characterizing the nonlinear mechanical behavior and pressure-sensitive characteristics of rock and soil are verified; the discrete element parameters calibrated by this method can be simultaneously applied to triaxial compression numerical tests of rock and soil under different confining pressures; the triaxial compression mechanical behavior of the rock and soil under any confining pressure in the maximum and minimum confining pressure range can be predicted.

[0073] In one embodiment, a process of determining a nonlinear dynamic mapping relationship between a rock and soil elastic modulus and a spherical stress is introduced. Step 102 includes:

[0074] Step 1021, analyzing the stress-strain curve under a single confining pressure to determine the deformation characteristics of multiple deformation stages of the full compression process under a single confining pressure.

[0075] Among them, the multiple deformation stages include compaction stage, elastic deformation stage, pre-peak plastic deformation stage, post-peak plastic deformation stage and residual strength stage. The stress-strain curve is generally S-shaped before reaching the peak value, and the compaction stage and the elastic deformation stage show nonlinear deformation characteristics.

[0076] Step 1022, analyzing stress-strain curves under different confining pressures to determine deformation characteristics of the rock and soil under different confining pressures.

[0077] For example, by analyzing the stress-strain curves under different confining pressures, it is found that the stress-strain curve under high confining pressure is an envelope curve relative to that under low confining pressure. As the confining pressure increases, the overall deformation of the rock and soil increases significantly, and the elastic and plastic deformation limits increase significantly; the elastic modulus and peak strength of the rock and soil are significantly improved, its ductility increases, and its brittleness decreases, and the rock and soil shows typical pressure-sensitive characteristics.

[0078] Step 1023, based on the nonlinear deformation characteristics of the compaction stage and the elastic deformation stage in the full compression process under a single confining pressure and the deformation characteristics of the rock and soil under different confining pressures, determine the nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil in the compaction stage and the elastic deformation stage under different confining pressures and the change of the spherical stress.

[0079] For example, the functional relationship between the secant modulus and the spherical stress is constructed: the elastic modulus and the spherical stress in the process of reaching the maximum slope in the full-process stress-strain curve under different confining pressures are extracted, such as Figure 4 The nonlinear dynamic mapping relationship between the elastic modulus of rock and soil in the compaction stage and the elastic deformation stage under different confining pressures and the change of spherical stress is an exponential correlation, and the correlation coefficient can reach 99%.

[0080] Elastic modulus of rock and soil in compaction stage and elastic deformation stage under different confining pressures E The nonlinear dynamic mapping relationship with the change of spherical stress can be expressed as:

[0081]

[0082] in, is the maximum value of elastic modulus; Represents the change in elastic modulus, that is, the initial value of the elastic modulus The maximum value of elastic modulus The difference between Represents the hardening speed. Under the same stress, the larger the value, the slower the hardening. Spherical stress includes stress in the vertical direction. and horizontal stress .

[0083] This embodiment can accurately capture multiple deformation stages of rock and soil during the full compression process by analyzing the stress-strain curves under a single confining pressure and different confining pressures in detail, which helps to more accurately understand the mechanical behavior of rock and soil, thereby improving the accuracy of the prediction of the elastic modulus of rock and soil in the compaction stage and elastic deformation stage under different confining pressures. By comparing the stress-strain curves under different confining pressures, the pressure-sensitive characteristics of rock and soil are revealed, that is, as the confining pressure increases, the deformation characteristics, elastic modulus, peak strength, ductility and brittleness of rock and soil will change. This in-depth understanding of the pressure-sensitive characteristics helps to more accurately evaluate the stability and safety of rock and soil in complex stress environments.

[0084] Based on the above analysis, this method can establish a nonlinear dynamic mapping relationship between the elastic modulus of rock and soil in the compaction stage and elastic deformation stage under different confining pressures and the change of spherical stress. This mapping relationship not only takes into account the static mechanical properties of rock and soil, but also its dynamic change process, providing a powerful tool for dynamic analysis and design of geotechnical engineering.

[0085] In one embodiment, a process of establishing a three-dimensional particle flow discrete element numerical model at a microscopic scale is introduced. Step 103 includes:

[0086] Based on the nonlinear dynamic mapping relationship between the elastic modulus of rock and soil and the spherical stress, spherical particles with a preset radius range are selected using PFC3D software, such as Figure 5 The PFC3D triaxial compression specimen particles shown in the figure ignore the delicate microscopic crystal structure inside the rock and soil, and establish a three-dimensional particle flow discrete element numerical model on a microscopic scale.

[0087] Exemplarily, the nonlinear dynamic mapping relationship between the elastic modulus of rock and soil and the change of spherical stress is the nonlinear dynamic mapping relationship between the elastic modulus of rock and soil and the change of spherical stress in the compaction stage and the elastic deformation stage under different confining pressures in the above embodiment. A three-dimensional particle flow discrete element numerical model of a cuboid with an aspect ratio of 2:1 is established using PFC3D.

[0088] In one embodiment, a process of performing secondary opening of a three-dimensional particle flow discrete element numerical model based on a PB contact model is introduced, and step 104 includes:

[0089] Firstly, the linear spring and the bonded spring are set to act independently in the PB contact model, and the contact parameters are defined.

[0090] The contact parameters include linear spring stiffness, bonding spring stiffness and particle friction coefficient. Figure 6 As shown, Figure 6 (a) is a schematic diagram of the structure of two particles cemented together. Figure 6 (b) is a schematic diagram of the cemented contact of the PB contact model; Figure 6 (c) in the figure is a schematic diagram of the PB contact model without bonding; the main contact parameters defined are shown in Table 1. Different contact parameter values ​​correspond to different properties of rock and soil.

[0091] Table 1 Main contact parameters of PB contact model

[0092]

[0093] in, is the normal stiffness of the linear spring, which is used in the program express, is the tangential stiffness of the linear spring, which is used in the program It indicates that the value in the PB contact model is constant; is the normal stiffness of the bonded spring, which is used in the program express, is the tangential stiffness of the bonded spring, which is used in the program It indicates that the value in the PB contact model is constant; is the friction coefficient of the particles, which can affect the post-peak characteristics and is used in the program express; is the bonding cohesion of the bonded spring, which is used in the program express, is the bonding friction angle of the bonded spring, which is used in the program It is used to control the shear strength of the bonded spring.

[0094] Then, in the three-dimensional particle flow discrete element numerical model, the VSPB contact model that actively changes stiffness according to the stress environment is determined based on the linear spring stiffness and the bond spring stiffness; the VSPB contact model includes the functional relationship between the real-time spring stiffness and the contact stress of the rock and soil in the elastic stage; the VSPB contact model is used to traverse the contact status of all particles and update the contact stiffness of the particles based on the contact status of the particles.

[0095] For example, in the particle discrete element numerical simulation, the deformation modulus of rock and soil in the compaction stage and elastic deformation stage is mainly determined by the linear spring stiffness and cementation spring stiffness in the discrete element parameters, so these stiffness values ​​are also related to the stress environment. The real-time spring stiffness of rock and soil in the elastic stage is also exponentially related to the contact stress. Contact stress The functional relationship is expressed as:

[0096]

[0097] in, is the initial value of the normal stiffness of the bonded spring, which is a constant term; is the maximum value of the normal stiffness of the bonded spring, which is a constant term; To define the hardening coefficient, is a constant term. , , The values ​​of these constants control the functional relationship between the spring stiffness and the contact stress. Different properties of rock and soil correspond to different parameter values.

[0098] Exemplarily, the contact states of all particles include a first contact state, a second contact state, and a third contact state. The first contact state is that the bonding is not broken, and the contact stress of the particles is greater than 0; the second contact state is that the bonding is broken, the contact stress of the particles is greater than 0, and the contact stress of the particles is not decayed; the third contact state is that the bonding is broken, the contact stress of the particles is greater than 0, and the contact stress of the particles decays to the first preset multiple of the last contact stress of the particles. K 1.

[0099] Exemplarily, updating the contact stiffness of the particles based on the contact state of the particles includes:

[0100] When the contact state of the particles is the first contact state, the bonding spring stiffness and the linear spring stiffness are updated. The bonding spring stiffness includes the normal stiffness of the bonding spring and the tangential stiffness of the bonding spring; the linear spring stiffness includes the normal stiffness of the linear spring and the tangential stiffness of the linear spring.

[0101] When the contact state of the particles is the second contact state, the linear spring stiffness is kept constant.

[0102] When the contact state of the particle is the third contact state, the linear spring stiffness is multiplied by the second preset multiple. K 2 Perform post-peak linear spring rate decay.

[0103] Among them, the first preset multiple K 1 is the stiffness attenuation trigger coefficient. The larger the value, the earlier the post-peak particle stiffness attenuation is triggered. The smaller the value, the later the trigger is and the longer the ductility platform section is. The value range is (0,1). The second preset multiple K 2 is the post-peak stiffness attenuation coefficient, and its value range is (0,1).

[0104] Traverse the contact states of all particles, define callback functions and then group the contact states of all particles through judgment statements, and update the particle contact stiffness according to the different rules corresponding to the above different states. In the process of updating the contact stiffness of particles, generally set = , while introducing Coefficient (linear bonding stiffness coefficient) = linear spring stiffness / bonding spring stiffness, at this time, , , , Therefore, when the contact stiffness of the particles is When updating according to the contact state and stress environment of the particles, , and Also updated accordingly.

[0105] You can set the update frequency , that is, every time the operation step is , run once and the parameters will be updated accordingly.

[0106] This embodiment can more accurately simulate the actual behavior of geotechnical materials during stress by distinguishing between the first contact state (unbroken bonding), the second contact state (broken bonding but unattenuated stress), and the third contact state (broken bonding and attenuated stress). Different contact states correspond to different mechanical responses, thereby improving the accuracy and authenticity of the simulation. Different geotechnical materials have different mechanical properties, such as stiffness and strength. By setting different contact states, the changes in these properties during stress can be better reflected. For example, for geotechnical materials with greater stiffness, the stiffness value in the unbroken bonding state is higher; while for materials with lower strength, bonding failure may occur under smaller stresses.

[0107] The introduction of the linear bond stiffness coefficient (i.e., the ratio of the linear spring stiffness to the bond spring stiffness) can combine two independent stiffness parameters into one, thereby simplifying the setting of model parameters. This not only reduces the complexity of parameter setting, but also helps to improve simulation efficiency. By adjusting the linear bond stiffness coefficient, the mechanical properties of different geotechnical materials can be adapted. This makes the model more applicable and flexible when simulating different types of geotechnical materials. Setting a suitable update frequency can ensure that the mechanical response of the geotechnical material after being subjected to force is reflected in a timely manner during the simulation process.

[0108] In one embodiment, the process of adjusting the contact parameters of the VSPB contact model and calibrating the parameters is introduced with the macroscopic mechanical parameters of the rock and soil as the target. Step 105 includes:

[0109] (1) Selection of working conditions: The triaxial compression test of rock and soil generally adopts multiple confining pressure conditions, and the debugging is relatively cumbersome. When adjusting the parameters, two groups of working conditions, low confining pressure and high confining pressure, are selected first.

[0110] (2) Parameter adjustment: The principle of parameter calibration is usually qualitative first and then quantitative. , which can change the curve shape at the peak. The larger the value, the higher the weight of the linear spring stiffness, the smaller the loss of stiffness when the bond fails, and the macroscopic performance is ductile failure; the smaller the coefficient value, the macroscopic performance is brittle failure.

[0111] Adjust the initial value of the bond spring normal stiffness , the larger the value, the greater the elastic modulus at the compaction stage and elastic deformation stage at the macro level The larger the value, the greater the maximum value of the normal stiffness of the bonded spring. , the larger the value, the higher the elastic modulus at the macro level The larger the value, the harder the coefficient The smaller the value, the faster the stiffness increases under the same stress conditions; adjust the bonding cohesion of the bonded spring and the bonded friction angle of the bonded spring , to ensure that the peak strength matches the indoor test; adjust the friction coefficient of the particles , which affects the mechanical behavior of the material after reaching the stress peak. The larger the friction coefficient, the higher the post-peak strength at the macro level. Update frequency The smaller it is, the smoother the stress-strain curve of the numerical test is. After repeated debugging, the mechanical parameters of the numerical specimens are consistent with those of the real geotechnical specimens.

[0112] According to experience, it may take about 30 trials to obtain a good parameter. The calculation speed of the model is related to factors such as time scale, number of particles and computer configuration.

[0113] The geotechnical mechanics characterization method based on particle flow discrete element numerical simulation in the embodiment of the present application obtains the compressive stress-strain curve of the rock and soil under different confining pressures on the macro scale through indoor rock and soil triaxial compression tests, ensuring the authenticity and reliability of the test data and providing a solid foundation for subsequent analysis. The compressive stress-strain curve of the rock and soil under different confining pressures is analyzed to determine the nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil and the change of spherical stress, revealing the mechanical properties of the rock and soil under multi-dimensional stress states, and providing a theoretical basis for establishing a numerical model on the micro scale. Based on the above nonlinear dynamic mapping relationship, a three-dimensional particle flow discrete element numerical model on the micro scale is established, which can reproduce the pre-peak nonlinear deformation mechanical behavior of the rock and soil under a specific confining pressure, and at the same time reproduce the pressure-sensitive characteristics of the rock and soil, converting the test results on the macro scale into a numerical model on the micro scale, realizing the leap from macro to micro. Based on the PB contact model, the three-dimensional particle flow discrete element numerical model was secondary developed, and the active variable stiffness linear parallel bonding model VSPB contact model, which can update the discrete element contact parameters in real time during the loading process, was constructed. The contact parameters of the VSPB contact model were adjusted with the macroscopic mechanical parameters of the rock and soil as the target, and finally the discrete element parameters that can reflect the mechanical properties of the rock and soil can be obtained, which improves the accuracy and applicability of the numerical model. Through a series of rigorous and scientific steps, the problems existing when the parameters calibrated based on the uniaxial compression test are directly applied to the triaxial compression numerical simulation are effectively solved, providing strong support for the in-depth research and practical application of rock and soil mechanics.

[0114] See also Figure 7 The embodiment of the present application provides a geotechnical mechanics characterization device based on particle flow discrete element numerical simulation, which executes the geotechnical mechanics characterization method based on particle flow discrete element numerical simulation as in the above embodiment, including an experimental data acquisition module 201, a mapping relationship analysis module 202, a model building module 203, a secondary development module 204, a model optimization module 205 and an actual output module 206.

[0115] The experimental data acquisition module 201 is used to obtain the compressive stress-strain curve of the rock and soil under different confining pressures on a macro scale by using a rock and soil triaxial compression test indoors;

[0116] A mapping relationship analysis module 202 is used to analyze the compressive stress-strain curve of rock and soil under different confining pressures and determine the nonlinear dynamic mapping relationship between the elastic modulus of rock and soil and the change of spherical stress;

[0117] The model building module 203 is used to build a three-dimensional particle flow discrete element numerical model on a microscopic scale based on the nonlinear dynamic mapping relationship between the rock and soil elastic modulus and the spherical stress;

[0118] A secondary development module 204 is used to perform secondary development on the three-dimensional particle flow discrete element numerical model based on the PB contact model to obtain a VSPB contact model that actively changes stiffness according to the stress environment;

[0119] The model optimization module 205 is used to adjust the contact parameters of the VSPB contact model with the macroscopic mechanical parameters of the rock and soil as the target, and determine the optimized VSPB contact model based on the contact parameters of the VSPB contact model;

[0120] The actual output module 206 is used to determine the final compressive stress-strain curve of the rock and soil by using triaxial numerical tests based on the optimized VSPB contact model.

[0121] For the beneficial effects of the geotechnical mechanics characterization device based on particle flow discrete element numerical simulation, please refer to the beneficial effects of a geotechnical mechanics characterization method based on particle flow discrete element numerical simulation.

[0122] The present application also provides a controller, see Figure 8 The controller 700 may include: at least one processor 710 and a memory 720, wherein the memory 720 stores a computer program that can be run on the at least one processor 710, and when the processor 710 executes the computer program, the steps in any of the above method embodiments are implemented.

[0123] Exemplarily, the computer program may be divided into one or more modules / units, one or more modules / units are stored in the memory 720, and executed by the processor 710 to complete the present application. One or more modules / units may be a series of computer program segments capable of completing specific functions, and the program segments are used to describe the execution process of the computer program in the controller 700.

[0124] Those skilled in the art will understand that Figure 8 These are merely examples of controllers and do not constitute a limitation of the controller, which may include more or fewer components than those shown in the figure, or a combination of certain components, or different components, such as input and output devices, network access devices, buses, etc.

[0125] The processor 710 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0126] The memory 720 may be an internal storage unit of the controller or an external storage device of the controller, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. The memory 720 is used to store computer programs and other programs and data required by the server and the processor. The memory 720 may also be used to temporarily store data that has been output or is to be output.

[0127] 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. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus in the drawings of this application is not limited to only one bus or one type of bus.

[0128] The geotechnical mechanics characterization method based on particle flow discrete element numerical simulation provided in the embodiment of the present application can be applied to controllers such as computers, tablet computers, laptops, netbooks, personal digital assistants (PDAs), etc. The embodiment of the present application does not impose any restrictions on the specific type of controller.

[0129] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0130] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A geotechnical mechanics characterization method based on particle flow discrete element numerical simulation, characterized in that: include: Using triaxial compression test of rock and soil indoors, the compressive stress-strain curve of rock and soil under different confining pressures on a macro scale is obtained; Analyze the compressive stress-strain curves of the rock and soil under the different confining pressures, and determine the nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil and the change of the spherical stress; The analyzing the compressive stress-strain curve of the rock and soil under the different confining pressures to determine the nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil and the change of the spherical stress includes: Analyze the stress-strain curve under a single confining pressure to determine the deformation characteristics of multiple deformation stages in the full compression process under a single confining pressure; the multiple deformation stages include a compaction stage, an elastic deformation stage, a pre-peak plastic deformation stage, a post-peak plastic deformation stage, and a residual strength stage; the compaction stage and the elastic deformation stage present nonlinear deformation characteristics; Analyze the stress-strain curves under different confining pressures to determine the deformation characteristics of rock and soil under different confining pressures; Based on the nonlinear deformation characteristics of the compaction stage and the elastic deformation stage in the full compression process under the single confining pressure and the deformation characteristics of the rock and soil under different confining pressures, a nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil in the compaction stage and the elastic deformation stage under different confining pressures and the change of spherical stress is determined; Based on the nonlinear dynamic mapping relationship between the rock and soil elastic modulus and the spherical stress, a three-dimensional particle flow discrete element numerical model on a microscopic scale is established; The three-dimensional particle flow discrete element numerical model is secondary developed based on the PB contact model to obtain a VSPB contact model that actively changes stiffness according to the stress environment; the PB contact model is a linear parallel bonding model; the VSPB contact model is an active variable stiffness linear parallel bonding model; the three-dimensional particle flow discrete element numerical model is secondary developed based on the PB contact model to obtain a VSPB contact model that actively changes stiffness according to the stress environment, including: In the PB contact model, the linear spring and the cementation spring are set to act independently, and the contact parameters are defined; the contact parameters include the linear spring stiffness, the cementation spring stiffness and the friction coefficient of the particles; different contact parameter values ​​correspond to different properties of rock and soil; In the three-dimensional particle flow discrete element numerical model, the VSPB contact model that actively changes stiffness according to the stress environment is determined based on the linear spring stiffness and the bonding spring stiffness; the VSPB contact model includes the functional relationship between the real-time spring stiffness and the contact stress of the rock and soil in the compaction stage and the elastic deformation stage under different confining pressures; the VSPB contact model is used to traverse the contact states of all particles and update the contact stiffness of the particles based on the contact states of the particles; Taking the macroscopic mechanical parameters of rock and soil as a target, adjusting the contact parameters of the VSPB contact model, and determining an optimized VSPB contact model based on the contact parameters of the VSPB contact model; Based on the optimized VSPB contact model, the final compressive stress-strain curve of the rock and soil is determined by triaxial numerical tests.

2. The rock and soil mechanics characterization method based on particle flow discrete element numerical simulation according to claim 1 is characterized in that: The nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil in the compaction stage and the elastic deformation stage under different confining pressures and the change of spherical stress is an exponential correlation relationship.

3. The rock and soil mechanics characterization method based on particle flow discrete element numerical simulation according to claim 2 is characterized in that: Elastic modulus of rock and soil at the compaction stage and the elastic deformation stage under different confining pressures E The nonlinear dynamic mapping relationship with the change of spherical stress is expressed as: in, is the maximum value of elastic modulus; Represents the amplitude of change of elastic modulus; Represents the hardening rate; the spherical stress includes the stress in the vertical direction and horizontal stress .

4. The rock and soil mechanics characterization method based on particle flow discrete element numerical simulation according to claim 1, characterized in that: The three-dimensional particle flow discrete element numerical model on a microscopic scale is established based on the nonlinear dynamic mapping relationship between the rock and soil elastic modulus and the spherical stress, including: Based on the nonlinear dynamic mapping relationship between the elastic modulus of the rock and soil and the change of spherical stress, the PFC3D software was used to select spherical particles within a preset radius, and the delicate microscopic crystal structure inside the rock and soil was ignored to establish a three-dimensional particle flow discrete element numerical model on a microscopic scale.

5. The rock and soil mechanics characterization method based on particle flow discrete element numerical simulation according to claim 1 is characterized in that: Real-time spring stiffness of rock and soil in the compaction stage and the elastic deformation stage under different confining pressures Contact stress The functional relationship is expressed as: in, is the initial value of the normal stiffness of the bonded spring; is the maximum value of the normal stiffness of the bonded spring; To define the hardening coefficient.

6. The rock and soil mechanics characterization method based on particle flow discrete element numerical simulation according to claim 1, characterized in that: The contact states of all particles include a first contact state, a second contact state and a third contact state; The first contact state is that the bonding is not broken and the contact stress of the particles is greater than 0; The second contact state is cementation failure, the contact stress of the particles is greater than 0, and the contact stress of the particles is not attenuated; The third contact state is bonding failure, the contact stress of the particles is greater than 0, and the contact stress of the particles decays to a first preset multiple of the last contact stress of the particles.

7. The rock and soil mechanics characterization method based on particle flow discrete element numerical simulation according to claim 6 is characterized in that: The updating of the contact stiffness of the particle based on the contact state of the particle comprises: When the contact state of the particles is the first contact state, updating the bonding spring stiffness and the linear spring stiffness; When the contact state of the particles is the second contact state, the linear spring stiffness maintains a constant value; When the contact state of the particles is the third contact state, the post-peak linear spring stiffness is attenuated by multiplying the linear spring stiffness by a second preset multiple.

8. A controller, characterized in that: Execute the geotechnical mechanics characterization method based on particle flow discrete element numerical simulation as described in any one of claims 1 to 7.

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