Simulation method of frozen soil binary medium discrete element contact model

Abstract

The invention discloses a simulation method of a frozen soil binary medium discrete element contact model, which comprises the following steps of: establishing the frozen soil binary medium discrete element contact model among frozen soil particles according to whether cemented failure occurs or not; the frozen soil binary medium discrete element contact model between frozen soil particles only takes effect on the generalized Kelvin body cementation model; after cementation failure occurs, only a linear model of the frozen soil binary medium discrete element contact model among frozen soil particles takes effect; loading the established frozen soil binary medium discrete element contact model between frozen soil particles; performing double-ball single-contact simulation according to the loaded frozen soil binary medium discrete element contact model; and performing triaxial compression creep simulation and verification according to the loaded frozen soil binary medium discrete element contact model. The model provided by the invention not only can reflect the cementation effect among frozen soil particles and simulate the accelerated creep of a frozen soil material, but also can accurately simulate the initial creep and stable creep of the frozen soil material, and provides reference for the micromechanism research of frozen soil creep damage.

Description

Technical Field

[0001] The present invention relates to a simulation method for a discrete element contact model of frozen soil binary medium, and belongs to the field of numerical simulation of frozen soil creep discrete element. Background Art

[0002] Frozen soil is a composite material composed of soil particle matrix, ice crystals, unfrozen water and gas. Due to the existence of ice crystals in frozen soil, frozen soil has strong rheological properties. Therefore, the mechanical properties and deformation properties of frozen soil are more complex than those of unfrozen soil. The strength properties and deformation properties of frozen soil are closely related to the micro and meso structures of frozen soil.

[0003] Computational methods based on continuum, such as the finite element method, have advantages in the calculation of large-scale engineering problems, but they cannot describe the heterogeneity or internal failure mechanism of materials. Therefore, the discrete element method has more advantages in the study of meso mechanics of materials. The discrete element method assumes that materials are composed of particles that interact at the contact points, and simulates the deformation and failure processes of materials through the translation and rotation of particles. The force-displacement relationship between particles is called the contact model. Therefore, selecting a suitable contact model in discrete element numerical simulation is the key to accurately simulating the mechanical behavior of materials. In discrete element numerical simulation, the Burgers model is often used to simulate the creep characteristics of frozen soil materials. The Burgers model is a viscoelastic model composed of multiple springs and viscous elements, which can describe the initial creep and steady creep of frozen soil materials. However, the Burgers model cannot simulate the accelerating creep of frozen soil materials, nor can it reflect the cementation effect between frozen soil particles. Therefore, it has obvious limitations. In recent years, some scholars have developed a creep contact model that can reflect the cementation between frozen soil particles. This model can simulate the accelerating creep of frozen soil materials, but it cannot simulate the initial creep and steady creep of frozen soil materials well.

[0004] Based on the deficiencies of the above background art, the present invention is specifically proposed. Summary of the Invention

[0005] Aiming at the deficiencies of the current contact model in the numerical simulation of frozen soil creep discrete element, the present invention provides a simulation method for a discrete element contact model of frozen soil binary medium.

[0006] The technical solution of the present invention is as follows:

[0007] A simulation method for a discrete element contact model of frozen soil binary medium, comprising the following steps:

[0008] S1: Establish a discrete element contact model of dual - medium frozen soil between frozen soil particles based on whether cementation failure occurs. Before cementation failure occurs, only the generalized Kelvin - body cementation model in the discrete element contact model of dual - medium frozen soil between frozen soil particles is effective. After cementation failure occurs, only the linear model in the discrete element contact model of dual - medium frozen soil between frozen soil particles is effective.

[0009] S2: Load the established discrete element contact model of dual - medium frozen soil between frozen soil particles.

[0010] S3: Conduct a double - sphere single - contact simulation according to the loaded discrete element contact model of dual - medium frozen soil.

[0011] S4: Conduct a triaxial compression creep simulation and verification according to the loaded discrete element contact model of dual - medium frozen soil.

[0012] Furthermore, the components of the normal - direction component and the shear - direction component of the generalized Kelvin - body cementation model are the same. They are both composed of a Kelvin model, an elastic element, and a cementation bond in series. Among them, a Kelvin model is composed of an elastic element and a viscous element in parallel.

[0013] Furthermore, the normal - direction component of the linear model is composed of an elastic element and a zero - tension element in series, and the shear - direction component of the linear model is composed of an elastic element and a sliding element in series.

[0014] Furthermore, the step S2 is specifically as follows:

[0015] S201: Establish an expression for the contact - force displacement relationship of the generalized Kelvin - body cementation model, establish an evolution formula for the cementation damage variable of the generalized Kelvin - body cementation model, and establish an expression for the contact - force displacement relationship of the linear model.

[0016] S202: Based on the established expression for the contact - force displacement relationship of the generalized Kelvin - body cementation model, the evolution formula for the cementation damage variable of the generalized Kelvin - body cementation model, and the expression for the contact - force displacement relationship of the linear model, perform secondary development on the built - in model source code of the simulation software.

[0017] S203: Compile the code after secondary development to obtain a dynamic - link library file and import it into the simulation software to achieve the loading of the discrete element contact model of dual - medium frozen soil between frozen soil particles.

[0018] Furthermore, in S201, the established expression for the contact - force displacement relationship in the normal direction of the generalized Kelvin - body cementation model is as follows:

[0019]

[0020] Wherein: is the total displacement in the normal direction of the generalized Kelvin body cementation model at time t, is the total displacement in the normal direction of the generalized Kelvin body cementation model at time t + 1, is the displacement of the viscous element of the Kelvin model in the normal direction of the generalized Kelvin body cementation model at time t, is the displacement of the viscous element of the Kelvin model in the normal direction of the generalized Kelvin body cementation model at time t + 1, is the magnitude of the contact force in the normal direction of the generalized Kelvin body cementation model at time t, is the magnitude of the contact force in the normal direction of the generalized Kelvin body cementation model at time t + 1, a n and b n and A n and B n are the first parameters.

[0021] Furthermore, in the S201, the expression of the contact force-displacement relationship in the shear direction of the established generalized Kelvin body cementation model is as follows:

[0022]

[0023] Wherein: is the total displacement in the shear direction of the generalized Kelvin body cementation model at time t, is the total displacement in the shear direction of the generalized Kelvin body cementation model at time t + 1, is the displacement of the viscous element of the Kelvin model in the shear direction of the generalized Kelvin body cementation model at time t, is the displacement of the viscous element of the Kelvin model in the shear direction of the generalized Kelvin body cementation model at time t + 1, is the magnitude of the contact force in the shear direction of the generalized Kelvin body cementation model at time t, is the magnitude of the contact force in the shear direction of the generalized Kelvin body cementation model at time t + 1, a s and b s and A s and B s are the second parameters.

[0024] Furthermore, in the S201, the evolution formula of the cementation damage variable of the established generalized Kelvin body cementation model is as follows:

[0025]

[0026]

[0027] In the formula: is the intermediate variable of the cementation damage variable at time t, is the intermediate variable of the cementation damage variable at time t + 1, D t+1 is the cementation damage variable at time t + 1, is the magnitude of the contact force in the normal direction of the generalized Kelvin body cementation model at time t, is the magnitude of the contact force in the normal direction of the generalized Kelvin body cementation model at time t + 1, is the magnitude of the contact force in the shear direction of the generalized Kelvin body cementation model at time t, is the magnitude of the contact force in the shear direction of the generalized Kelvin body cementation model at time t + 1, T, D max is the third parameter.

[0028] Furthermore, in the S201, the expression of the contact force-displacement relationship of the established linear model is as follows:

[0029]

[0030]

[0031] In the formula: is the magnitude of the contact force in the normal direction of the linear model at time t, is the magnitude of the contact force in the normal direction of the linear model at time t + 1, is the magnitude of the contact force in the shear direction of the linear model at time t, is the magnitude of the contact force in the shear direction of the linear model at time t + 1; is a mnemonic, Δδ n is the difference between the displacement in the normal direction at time t + 1 and the displacement in the normal direction at time t, Δδ s is the difference between the displacement in the shear direction at time t + 1 and the displacement in the shear direction at time t; μ is the fourth parameter.

[0032] In the above, the terms "first", "second", "third", and "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0033] The beneficial effects of the present invention are as follows: The cementation damage variable in the discrete element contact model of frozen soil binary medium established by the present invention can control the time of cementation failure of the model. Based on this, the discrete element contact model of frozen soil binary medium of the present invention can not only reflect the cementation effect between frozen soil particles, simulate the accelerated creep of frozen soil materials, but also accurately simulate the initial creep and steady creep of frozen soil materials, providing a reference for the study of the microscopic mechanism of frozen soil creep failure. Brief Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the steps of the simulation method of the discrete element contact model for frozen soil binary media in the embodiment;

[0035] Figure 2 It is a schematic diagram of the discrete element contact model for frozen soil binary media in the embodiment;

[0036] Figure 3 It is a schematic diagram of the secondary development of the source code in the embodiment;

[0037] Figure 4 and Figure 5 It is a schematic diagram of the double - sphere single - contact creep simulation in the embodiment;

[0038] Figure 6 and Figure 7 It is a schematic diagram of the double - sphere single - contact tensile simulation in the embodiment;

[0039] Figure 8 and Figure 9 It is a schematic diagram of the triaxial compression creep simulation in the embodiment.

[0040] Figure 10 It is a schematic diagram of the triaxial compression creep verification in the embodiment. Detailed Embodiment

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention. It should be noted that, without conflict, the embodiments and features in the embodiments of this application can be combined with each other arbitrarily.

[0042] Embodiment 1: As Figures 1 - 10 shown, the present invention provides a simulation method for a discrete element contact model of frozen soil binary media. Referring to Figure 1 , the simulation method of the discrete element contact model of frozen soil binary media includes the following steps:

[0043] S1: Establish a discrete element contact model for frozen soil binary media between frozen soil particles according to whether cementation failure occurs: Before cementation failure occurs, only the generalized Kelvin body cementation model in the discrete element contact model for frozen soil binary media between frozen soil particles becomes effective; after cementation failure occurs, only the linear model in the discrete element contact model for frozen soil binary media between frozen soil particles becomes effective;

[0044] S2: Load the established discrete element contact model of the binary frozen soil medium between frozen soil particles;

[0045] S3: Conduct double-sphere single-contact simulation based on the loaded discrete element contact model of the binary frozen soil medium;

[0046] S4: Conduct and verify triaxial compression creep simulation based on the loaded discrete element contact model of the binary frozen soil medium.

[0047] Furthermore, the component elements of the normal direction component and the shear direction component of the generalized Kelvin body cementation model are the same, both consisting of a Kelvin model, an elastic element, and a cementation bond connected in series. Among them, a Kelvin model is composed of an elastic element and a viscous element connected in parallel.

[0048] Furthermore, the normal direction component of the linear model is composed of an elastic element and a zero-tension element connected in series, and the shear direction component of the linear model is composed of an elastic element and a sliding element connected in series.

[0049] Refer to Figure 2 , for the discrete element contact model of the binary frozen soil medium between a frozen soil particle with a mass of m1 and a frozen soil particle (discrete element) with a mass of m2. In the initial state, that is, before cementation failure occurs, only the generalized Kelvin body cementation model in the discrete element contact model of the binary frozen soil medium between frozen soil particles takes effect. After cementation failure occurs, only the linear model in the discrete element contact model of the binary frozen soil medium between frozen soil particles takes effect.

[0050] In the initial state, the interaction between the frozen soil particles with mass \(m_1\) and the frozen soil particles with mass \(m_2\) is borne by the generalized Kelvin body cementation model. Specifically, the component in the vertical direction on the left side of the generalized Kelvin body cementation model, which is called the normal direction component here, bears the normal interaction between the frozen soil particles; the component in the horizontal direction on the right side of the generalized Kelvin body cementation model, which is called the shear direction component here, bears the shear interaction between the frozen soil particles. The constituent elements of the normal direction component and the shear direction component are the same, both are composed of a Kelvin model, an elastic element (such as a spring) and a cementation bond in series. Among them, a Kelvin model is composed of an elastic element and a viscous element (such as a dashpot) in parallel. The elastic element has an elastic effect, and its parameter can be represented by stiffness. There are a total of four elastic elements in the normal direction component and the shear direction component, and these four elastic elements have their respective stiffnesses. The viscous element has a damping effect, and its parameter can be represented by viscosity. There are a total of two viscous elements in the normal direction component and the shear direction component, and these two viscous elements have their respective viscosities. The stiffness of the elastic element and the viscosity of the viscous element are constants and do not change with time. The effect of the cementation bond is to judge whether the generalized Kelvin body cementation model is effective, and its parameter can be represented by the cementation damage variable. There are a total of two cementation bonds in the normal direction component and the shear direction component, and these two cementation bonds share a cementation damage variable, that is, when the cementation damage variable of the cementation bond in the normal direction component changes, it will cause the cementation damage variable of the cementation bond in the shear direction component to change together, and vice versa. The cementation damage variable increases with the increase of force and time. When the cementation damage variable reaches or exceeds the damage threshold, cementation failure occurs, causing the generalized Kelvin body cementation model to fail.

[0051] After the cementation failure occurs, the interaction between the frozen soil particles with mass \(m_1\) and the frozen soil particles with mass \(m_2\) is borne by the linear model. Specifically, the component in the vertical direction on the left side of the linear model, which is called the normal direction component here, bears the normal interaction between the frozen soil particles; the component in the horizontal direction on the right side of the linear model, which is called the shear direction component here, bears the shear interaction between the frozen soil particles. The normal direction component is composed of an elastic element and a tensionless element in series, and the shear direction component is composed of an elastic element and a sliding element in series. The effect of the tensionless element is that it cannot bear tension, and its parameter can be represented by the maximum surface gap value. The sliding element has a sliding effect, and its parameter can be represented by the friction coefficient. The maximum surface gap value of the tensionless element and the friction coefficient of the sliding element are constants and do not change with time.

[0052] Furthermore, step S2 is specifically as follows:

[0053] S201. Establish the expression of the contact force-displacement relationship of the generalized Kelvin body cementation model, establish the evolution formula of the cementation damage variable of the generalized Kelvin body cementation model, and establish the expression of the contact force-displacement relationship of the linear model;

[0054] S202. Secondary develop the built-in model source code of the simulation software according to the established expression of the contact force-displacement relationship of the generalized Kelvin body cementation model, the evolution formula of the cementation damage variable of the generalized Kelvin body cementation model, and the expression of the contact force-displacement relationship of the linear model;

[0055] S203. Compile the code after secondary development, obtain the dynamic link library file and import it into the simulation software to realize the loading of the binary medium discrete element contact model of frozen soil particles.

[0056] Furthermore, in the step S201, the expression of the contact force-displacement relationship in the normal direction of the established generalized Kelvin body cementation model is as follows:

[0057]

[0058] In the formula: is the total displacement in the normal direction of the generalized Kelvin body cementation model at time t, is the total displacement in the normal direction of the generalized Kelvin body cementation model at time t + 1, is the displacement of the viscous element of the Kelvin model in the normal direction of the generalized Kelvin body cementation model at time t, is the displacement of the viscous element of the Kelvin model in the normal direction of the generalized Kelvin body cementation model at time t + 1, is the magnitude of the contact force in the normal direction of the generalized Kelvin body cementation model at time t, is the magnitude of the contact force in the normal direction of the generalized Kelvin body cementation model at time t + 1, a n b n A n B n are parameters. a n b n A n B n The expressions of are as follows:

[0059]

[0060] Among them, is the stiffness of the elastic element in the normal direction of the generalized Kelvin body cementation model, is the stiffness of the elastic element of the Kelvin model in the normal direction of the generalized Kelvin body cementation model, is the viscosity of the viscous element of the Kelvin model in the normal direction of the generalized Kelvin body cementation model, and Δt represents the difference between the (t + 1)-th moment and the t-th moment.

[0061] Furthermore, in the step S201, the expression of the contact force-displacement relationship in the shear direction of the established generalized Kelvin body cementation model is as follows:

[0062]

[0063] In the formula: is the total displacement in the shear direction of the generalized Kelvin body cementation model at the t-th moment, is the total displacement in the shear direction of the generalized Kelvin body cementation model at the (t + 1)-th moment, is the displacement of the viscous element of the Kelvin model in the shear direction of the generalized Kelvin body cementation model at the t-th moment, is the displacement of the viscous element of the Kelvin model in the shear direction of the generalized Kelvin body cementation model at the (t + 1)-th moment, is the magnitude of the contact force in the shear direction of the generalized Kelvin body cementation model at the t-th moment, is the magnitude of the contact force in the shear direction of the generalized Kelvin body cementation model at the (t + 1)-th moment, a s 、b s 、A s 、B s are parameters. a s 、b s 、A s 、B s The expressions of are as follows:

[0064]

[0065] Among them, is the stiffness of the elastic element in the shear direction of the generalized Kelvin body cementation model, is the stiffness of the elastic element of the Kelvin model in the shear direction of the generalized Kelvin body cementation model, is the viscosity of the viscous element of the Kelvin model in the shear direction of the generalized Kelvin body cementation model, and Δt represents the difference between the (t + 1)-th moment and the t-th moment.

[0066] Furthermore, in the step S201, the evolution formula of the cementation damage variable of the established generalized Kelvin body cementation model is as follows:

[0067]

[0068]

[0069] Wherein: is the intermediate variable of the cementation damage variable at time t, is the intermediate variable of the cementation damage variable at time t + 1, D t+1 is the cementation damage variable at time t + 1, is the magnitude of the contact force in the normal direction of the generalized Kelvin body cementation model at time t, is the magnitude of the contact force in the normal direction of the generalized Kelvin body cementation model at time t + 1, is the magnitude of the contact force in the shear direction of the generalized Kelvin body cementation model at time t, is the magnitude of the contact force in the shear direction of the generalized Kelvin body cementation model at time t + 1, T, D max are parameters, and ∧ represents and.

[0070] Furthermore, in the step S201, the expression of the contact force-displacement relationship of the established linear model is as follows:

[0071]

[0072]

[0073]

[0074] Wherein: is the magnitude of the contact force in the normal direction of the linear model at time t, is the magnitude of the contact force in the normal direction of the linear model at time t + 1, is the magnitude of the contact force in the shear direction of the linear model at time t, is the magnitude of the contact force in the shear direction of the linear model at time t + 1; is a mnemonic, Δδ n is the difference between the displacement in the normal direction at time t + 1 and the displacement in the normal direction at time t, Δδ s is the difference between the displacement in the shear direction at time t + 1 and the displacement in the shear direction at time t; μ is a parameter.

[0075] Further, in step S202, a secondary development compilation environment for the PFC contact model is built using Visual Studio 2017, Qt5.12.0, and PFC. The source code of the built-in model in the PFC help document is imported into the header file (.h file) and source file (.cpp file) of Visual Studio 2017. Since the discrete element contact model for frozen soil binary media includes the generalized Kelvin body cementation model and the linear model, the source code of the Burgers model and the Soft-Bond model in the PFC software built-in model is selected for secondary development in Visual Studio 2017: Refer to Figure 3 , specifically, the bond method in the Soft-Bond model is introduced into the Burgers model, and the force-displacement law of the Burgers model is modified to "establish a judgment condition based on the cementation damage variable, and select the contact force-displacement relationship expression of the generalized Kelvin body cementation model or the contact force-displacement relationship expression of the linear model according to the judgment condition", and the cementation damage variable, etc. are set inside to obtain the code after secondary development.

[0076] The establishment of the judgment condition based on the cementation damage variable is specifically: judge that the value of the cementation damage variable is greater than or equal to D max , when the value of the cementation damage variable is greater than or equal to D max is satisfied, select the contact force-displacement relationship expression of the linear model; otherwise, select the contact force-displacement relationship expression of the generalized Kelvin body cementation model.

[0077] In step S203, the code after secondary development is debugged in Visual Studio 2017 to generate a solution to obtain the compiled dynamic link library file (.dll file). By placing the dynamic link library file (.dll file) in the specified file directory, the PFC software can automatically identify and load the dynamic link library file (.dll file).

[0078] In step S3, refer to Figure 4 and Figure 5, the double-sphere single-contact creep simulation is carried out according to the discrete element contact model of frozen soil binary medium. Initially, the gap between the two spherical particles is zero. The discrete element contact model of frozen soil binary medium is assigned between the two spherical particles. The lower spherical particle is fixed, and a constant vertically upward force is applied to the upper spherical particle for a certain period of time. Since only the generalized Kelvin body cementation model takes effect before the cementation failure in the discrete element contact model of frozen soil binary medium, there is a cementation effect. Although there is a gap between the two spherical particles due to the applied force, there is still an interaction between the two spherical particles. In the displacement-time relationship, the instantaneous displacement reflects the characteristics of the elastic element, and the displacement varying with time reflects the Kelvin model, that is, the characteristics of the parallel connection of the elastic element and the viscous element. As Figure 5 shown in the cementation damage variable-time relationship, the cementation damage variable Damage increases with time and approaches the damage threshold D max .

[0079] Referring to Figure 6 and Figure 7 , the double-sphere single-contact tension simulation is carried out according to the discrete element contact model of frozen soil binary medium. Initially, the gap between the two spherical particles is zero. The discrete element contact model of frozen soil binary medium is assigned between the two spherical particles. The lower spherical particle is fixed, and a constant vertically upward velocity is applied to the upper spherical particle for a certain period of time. Since only the generalized Kelvin body cementation model takes effect before the cementation failure in the discrete element contact model of frozen soil binary medium, there is a cementation effect. Although there is a gap between the two spherical particles due to the applied velocity, there is still an interaction between the two spherical particles. In the contact force-time relationship, the contact force increases with time. As Figure 7 shown in the cementation damage variable-time relationship, the cementation damage variable does not increase when the contact force is less than the tension threshold , and when the contact force is greater than the tension threshold, the cementation damage variable increases with time and approaches the damage threshold. As the loading progresses, the cementation damage variable reaches the damage threshold and stops changing, and the cementation fails. Only the linear model takes effect after the cementation failure in the discrete element contact model of frozen soil binary medium. Therefore, the contact force between the two spherical particles becomes zero, that is, there is no tension.

[0080] In step S4, referring to Figure 8 and Figure 9, the triaxial compression creep simulation is carried out according to the discrete element contact model of frozen soil binary medium. A cylindrical specimen with a height of 125 mm and a diameter of 61.8 mm is established. The specimen has a total of 6227 particles, and the radius range of the particles is 1.0 - 3.0 mm. The porosity of the specimen is 0.3. The discrete element contact model of frozen soil binary medium is assigned to the particles in contact with the particle specimen. The wall under the particle specimen is fixed. A confining pressure of 1.4 MPa is applied to the particle specimen by the cylindrical wall, and a constant vertical downward force is applied to the particle specimen by the upper wall to make the deviator stress of the particle specimen reach 7.67 MPa. In the relationship between axial strain - time, an instantaneous strain appears in the particle specimen at the beginning. As time increases, the particle specimen changes from initial creep to steady creep and finally enters accelerating creep. In the relationship between the number of cementation failures - time, there are no cementation failures in the initial period. As time increases, the number of cementation failures gradually increases. It can be seen that the creep stage of the particle specimen is related to the number of cementation failures of the particle specimen, and the number of cementation failures of the particle specimen is related to the cementation damage variable. Therefore, the cementation damage variable can control each stage of the creep of the particle specimen.

[0081] Refer to Figure 10 , the triaxial compression creep verification is carried out according to the discrete element contact model of frozen soil binary medium. Through the trial - and - error method, the parameters of the discrete element contact model of frozen soil binary medium are continuously adjusted to make the axial strain - time curve in the triaxial compression creep simulation match the laboratory test data, and compare with the numerical simulation results of the existing creep contact models that can reflect the cementation between frozen soil particles. The solid line is the laboratory test result, the dash line is the simulation result of the discrete element contact model of frozen soil binary medium (i.e., the numerical simulation result of this model), and the dotted line is the simulation result of the existing creep contact model. It can be seen that the discrete element contact model of frozen soil binary medium can more accurately simulate the initial creep, steady creep and accelerating creep of frozen soil.

[0082] In the embodiments of the present invention, the values of the parameters for the discrete element numerical simulation according to the loaded discrete element contact model of frozen soil binary medium are shown in Table 1:

[0083] Table 1 Parameters of the discrete element contact model of frozen soil binary medium

[0084]

[0085]

[0086] Among the above - mentioned parameters, and μ are positive constants, T≥0, 0≤D max ≤1.

[0087] Applying the above technical solution, it can be seen that the cementation damage variable in the discrete element contact model of frozen soil binary medium established in the present invention can control the time of cementation failure of the model. Therefore, the discrete element contact model of frozen soil binary medium can not only reflect the cementation effect between frozen soil particles, simulate the accelerated creep of frozen soil materials, but also more accurately simulate the initial creep and steady creep of frozen soil materials, providing a reference for the study of the microscopic mechanism of frozen soil creep failure.

[0088] The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A simulation method for a discrete element contact model of a frozen soil binary medium, characterized in that: The following steps are involved: S1: Based on whether the cementation failure occurs, a frozen soil binary medium discrete element contact model between frozen soil particles is established: before the cementation failure occurs, only the generalized Kelvin body cementation model is effective in the frozen soil binary medium discrete element contact model between frozen soil particles; after the cementation failure occurs, only the linear model is effective in the frozen soil binary medium discrete element contact model between frozen soil particles; S2: Loading the established frozen soil binary medium discrete element contact model between frozen soil particles; S3: Double-sphere single contact simulation based on the loaded frozen soil binary medium discrete element contact model; S4: Triaxial compression creep simulation and verification based on the loaded frozen soil binary medium discrete element contact model.

2. The simulation method of the frozen soil binary medium discrete element contact model according to claim 1 is characterized in that: The components of the normal direction component and the shear direction component of the generalized Kelvin body bonding model are the same, both of which are composed of a Kelvin model, an elastic element and a bonding bond in series, wherein a Kelvin model is composed of an elastic element and a viscous element in parallel.

3. The simulation method of the frozen soil binary medium discrete element contact model according to claim 1 is characterized in that: The normal direction component of the linear model is composed of an elastic element and a tension-free element connected in series, and the shear direction component of the linear model is composed of an elastic element and a sliding element connected in series.

4. The simulation method of the frozen soil binary medium discrete element contact model according to claim 1 is characterized in that: The step S2 is specifically: S201. Establish the contact force-displacement relationship expression of the generalized Kelvin body bonding model, establish the bonding damage variable evolution formula of the generalized Kelvin body bonding model, and establish the contact force-displacement relationship expression of the linear model; S202. Conduct secondary development of the source code of the built-in model of the simulation software based on the established contact force-displacement relationship expression of the generalized Kelvin body bonding model, the bonding damage variable evolution formula of the generalized Kelvin body bonding model, and the contact force-displacement relationship expression of the linear model; S203, compiling the code after secondary development, obtaining a dynamic link library file and importing it into the simulation software to realize the loading of the frozen soil binary medium discrete element contact model between frozen soil particles.

5. The simulation method of the frozen soil binary medium discrete element contact model according to claim 4 is characterized in that: In S201, the contact force displacement relationship expression in the normal direction of the generalized Kelvin body bonding model is as follows: Where: is the total displacement in the normal direction of the generalized Kelvin body cementation model at time t, is the total displacement in the normal direction of the generalized Kelvin body cementation model at time t+1, is the displacement of the viscous element of the Kelvin model in the normal direction of the generalized Kelvin body cementation model at time t, is the displacement of the viscous element of the Kelvin model in the normal direction of the generalized Kelvin body cementation model at time t+1, is the contact force in the normal direction of the generalized Kelvin body bonding model at time t, is the contact force in the normal direction of the generalized Kelvin body bonding model at time t+1, a n 、b n , A n , B n is the first parameter.

6. The simulation method of the frozen soil binary medium discrete element contact model according to claim 4 is characterized in that: In S201, the contact force displacement relationship expression in the shear direction of the generalized Kelvin body bonding model is as follows: Where: is the total displacement in the shear direction of the generalized Kelvin body cementation model at time t, is the total displacement in the shear direction of the generalized Kelvin body cementation model at time t+1, is the displacement of the viscous element of the Kelvin model in the shear direction of the generalized Kelvin body cementation model at time t, is the displacement of the viscous element of the Kelvin model in the shear direction of the generalized Kelvin body cementation model at time t+1, is the contact force in the shear direction of the generalized Kelvin body bonding model at time t, is the contact force in the shear direction of the generalized Kelvin body bonding model at time t+1, a s 、b s , A s , B s is the second parameter.

7. The simulation method of the frozen soil binary medium discrete element contact model according to claim 4 is characterized in that: In S201, the evolution formula of the bonding damage variable of the generalized Kelvin body bonding model is as follows: Where: is the intermediate variable of the bonding damage variable at time t, is the intermediate variable of the bonding damage variable at time t+1, D t+1 is the bonding damage variable at time t+1, is the contact force in the normal direction of the generalized Kelvin body bonding model at time t, is the contact force in the normal direction of the generalized Kelvin body bonding model at time t+1, is the contact force in the shear direction of the generalized Kelvin body bonding model at time t, is the contact force in the shear direction of the generalized Kelvin body bonding model at time t+1, T.D max Is the third parameter.

8. The simulation method of the frozen soil binary medium discrete element contact model according to claim 4 is characterized in that: In S201, the contact force displacement relationship expression of the established linear model is as follows: Where: is the contact force magnitude in the normal direction of the linear model at time t, is the contact force in the normal direction of the linear model at time t+1, is the contact force magnitude in the shear direction of the linear model at time t, is the contact force magnitude in the shear direction of the linear model at time t+1; is a mnemonic, Δδ n is the difference between the normal displacement at time t+1 and the normal displacement at time t, Δδ s is the difference between the shear direction displacement at time t+1 and the shear direction displacement at time t; μ is the fourth parameter.

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