Construction method of slip band soil three-dimensional creep constitutive model considering hardening-damage effect

Abstract

The invention provides a construction method of a slip band soil three-dimensional creep constitutive model considering a hardening-damage effect, and relates to the field of geotechnical engineering numerical calculation, and the method comprises the steps: obtaining an original slip band soil creep test result; constructing a hardening evolution equation and a damage evolution equation; constructing a seven-element creep model considering the hardening-damage effect through the hardening evolution equation and the damage evolution equation; on the basis of constant volume hypothesis and in combination with a seven-element creep model, a slip band soil three-dimensional creep constitutive model considering the hardening-damage effect is constructed; and according to the creep test result of the original-state slip band soil, solving the creep parameters of the slip band soil three-dimensional creep constitutive model by combining a staged test curve fitting method, and completing the construction of the slip band soil three-dimensional creep constitutive model. A hardening factor and a damage factor are respectively introduced into creep parameters to quantitatively characterize the strengthening and weakening effects of the rock-soil body performance in the creep process, and the creep mechanical behavior of the structural slip band soil can be accurately described.

Description

Technical Field

[0001] This application relates to the field of geotechnical engineering numerical calculations, and particularly to a method for constructing a three-dimensional creep constitutive model of slip zone soil considering hardening-damage effects. Background Art

[0002] The deformation of large accumulation layer landslides has predictable creep characteristics, which can be quantitatively described through the creep mechanism of the slip zone, but the premise is to fully understand the additional mechanical behavior generated by the natural slip zone structure and stress environment. The creep behavior of slip zone soil is jointly affected by hardening and damage effects. For the description of the creep behavior of structural slip zone soil, a creep-type viscoelastic constitutive model considering hardening and damage needs to be adopted. Currently, only simple linear viscoelastic constitutive models are included in commercial finite difference software, and the creep hardening-damage effects of structural slip zone soil cannot be accurately described.

[0003] With the development of high-precision test methods and numerical simulation technologies, a further understanding of the mesoscopic evolution process of the slip zone has been achieved, and it has been found that there are two effects of hardening and damage during the creep process. However, current research on the creep characteristics of the slip zone mainly focuses on the damage effect and ignores the hardening effect, which is manifested as the continuous compaction of pores and fractures. This phenomenon cannot be ignored during the compression process of undisturbed soil. The hardening effect of the slip zone occurs in the initial stage of deformation and, as an important mechanical property of structural slip zone soil, should be considered in the construction of the creep constitutive model.

[0004] Large landslides are complex systems, and numerical simulation remains a powerful means for evaluating and predicting landslide states. In the past, the prediction of long-term landslide deformation was mostly based on elastoplastic models or built-in creep models of software for analysis and calculation, and the mechanical behavior of landslides could not be accurately predicted. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for constructing a three-dimensional creep constitutive model of slip zone soil considering hardening-damage effects, in order to solve the problem that the prediction of long-term landslide deformation in the prior art is mostly based on elastoplastic models or built-in creep models of software for analysis and calculation, and the mechanical behavior of landslides cannot be accurately predicted.

[0006] The above object of this application is achieved through the following technical solutions:

[0007] S1: Obtain the creep test results of undisturbed slip zone soil;

[0008] S2: Construct a hardening evolution equation and a damage evolution equation;

[0009] S3: Construct a seven-element creep model considering hardening-damage effects through the hardening evolution equation and the damage evolution equation;

[0010] S4: Based on the constant volume assumption and combined with the seven-element creep model, a three-dimensional creep constitutive model of slip zone soil considering hardening-damage effect is constructed;

[0011] S5: According to the creep test results of undisturbed slip zone soil and combined with the method of fitting test curves in stages, the creep parameters of the three-dimensional creep constitutive model of slip zone soil are solved to complete the construction of the three-dimensional creep constitutive model of slip zone soil.

[0012] Optionally, step S2 includes:

[0013] The steps of analyzing the hardening-damage competition mechanism in the whole process of creep and constructing the hardening evolution equation are as follows:

[0014] It is assumed that the hardening effect of undisturbed slip zone soil starts at the instant of loading and ends at the stage of steady creep, satisfying that when the time approaches 0, the hardening factor H is 0, and when the time approaches infinity, the hardening factor H is a constant;

[0015] The hardening factor H is a function related to stress and time, then the hardening evolution equation is as follows:

[0016] H = e -λt -1 (1)

[0017] In the formula, λ is a parameter reflecting the strengthening degree of slip zone soil, that is, a stress-related parameter, which is obtained through the creep test results of undisturbed slip zone soil; t is the creep time.

[0018] Optionally, step S2 includes:

[0019] The steps of analyzing the hardening-damage competition mechanism in the whole process of creep and constructing the hardening evolution equation are as follows:

[0020] It is assumed that the hardening effect of undisturbed slip zone soil starts at the instant of loading and ends at the stage of steady creep, satisfying that when the time approaches 0, the hardening factor H is 0, and when the time approaches infinity, the hardening factor H is a constant;

[0021] The hardening factor H is a function related to stress and time, then the hardening evolution equation is as follows:

[0022] H = e -λt -1 (1)

[0023] In the formula, λ is a parameter reflecting the strengthening degree of slip zone soil, that is, a stress-related parameter, which is obtained through the creep test results of undisturbed slip zone soil; t is the creep time.

[0024] Optionally, step S3 includes:

[0025] The steps of analyzing the hardening-damage competition mechanism in the whole process of creep and constructing the damage evolution equation are as follows:

[0026] It is assumed that the damage effect of the original state slip zone soil rapidly increases at the end of the attenuation creep stage, and the damage effect is used to control the stable creep stage and the accelerating creep stage; assuming that the damage factor D is a piecewise function, the damage evolution equation is as follows:

[0027]

[0028] In the formula, q represents the deviator stress; σ y is the critical stress between the attenuation creep stage and the stable creep stage; α is a coefficient reflecting the damage degree of geotechnical materials, which is related to the stress σ; t is the creep time.

[0029] Step S3 also includes:

[0030] Introduce a hardening factor and a damage factor to correct the creep parameters, and form a seven-element creep model including a Hooke body, a hardening Kelvin body, and a hardening-damage Bingham body;

[0031] Construct a seven-element creep model considering the hardening-damage effect, specifically as follows:

[0032]

[0033] In the formula, σ represents the stress parameter; E0 represents the elastic modulus of the spring element; E1 represents the elastic modulus of the viscoelastic element; λ1 represents the stress-related coefficient in the hardening factor function introduced by the viscous element in the viscoelastic element; η1 represents the viscosity coefficient; t represents the creep time; σ y represents the critical stress between the attenuation creep stage and the stable creep stage, that is, the yield stress; ξ represents the coupling coefficient of damage and hardening; η2 represents the viscosity coefficient; σ s represents the long-term strength.

[0034] Optionally, step S4 includes:

[0035] The three-dimensional creep constitutive model of the slip zone soil considering the hardening-damage effect is specifically as follows:

[0036]

[0037] Among them, represents the deviator stress tensor, i and j represent different spatial directions. Usually in three-dimensional space, i, j ∈ {1, 2, 3}, corresponding to the x, y, and z directions respectively; σ m represents the spherical stress tensor; δ ij represents the Kronecker symbol; ε ij represents the total strain; and represent the strains of the Hooke body, the hardened Kelvin body, and the Bingham body with the coupling effect of hardening and damage respectively; δ ijis the Kronecker function; G0 represents the shear modulus of the spring element; K represents the bulk modulus of the spring element; G1 represents the shear modulus of the viscoelastic element; H1 represents the hardening factor introduced by the viscoelastic element; represents the switching function; F represents the switching function; F0 represents the initial value of the yield function; Q is the plastic potential function, when F≥0, Q = F; H2 represents the hardening factor introduced by the viscoplastic element; D1 represents the damage factor introduced by the viscoplastic element; σ ij represents the stress tensor;

[0038]

[0039] In the formula, x represents the exponent of the power function. For soil materials, F0 = 1 and x = 1; J2 represents the second invariant of the stress tensor; σ y represents the critical stress between the attenuation creep stage and the steady creep stage; σ1 represents the maximum principal stress; σ3 represents the maximum principal stress.

[0040] Optionally, step S5 includes:

[0041] According to the creep test results of the undisturbed slip zone soil, determine the creep parameters of the three-dimensional creep constitutive model of the slip zone soil; the creep parameters include: t0, G1, λ1, η1, σ y , ξ and η2;

[0042] Based on the characteristic points of the test curve, solve the creep parameters by the method of fitting the test curve in stages. The specific steps are as follows:

[0043] S51: Through the triaxial creep test, obtain the initial strain ε1 under different deviator stress levels. According to Equation (5), determine the shear modulus G0 and bulk modulus K under different confining pressures;

[0044] S52: When the deformation of the slip zone soil specimen enters the attenuation creep stage from the instantaneous strain stage and the creep time approaches infinity, the following relationship exists:

[0045]

[0046] where ε HK is the sum of the Hooke body strain and the hardened Kelvin body strain;

[0047] By fitting the data (t, F(t)), obtain the values of the shear modulus G1, the viscosity coefficient G1 and the coefficient λ1;

[0048] S53: The solution steps of the yield stress σ y , the viscosity coefficient η2 and the coefficient ξ are as follows:

[0049] When the sliding zone soil enters the steady creep stage from the decaying creep stage, the creep rate is a constant value, which is expressed as the first derivative of creep with respect to time, as follows:

[0050]

[0051] Yield stress σ y is the critical value between the decaying stage and the steady stage, that is, the first inflection point of the creep curve, and the creep curve is obtained from the creep test results of the undisturbed sliding zone soil;

[0052] Solving the viscosity coefficient η2 and the coefficient ξ specifically includes: taking n points (t i , ε i ) in the steady creep stage, where the value range of i is (1, n), and we get:

[0053]

[0054] where ξ i represents the ξ value at a certain t i time in the steady creep stage; t i represents a certain time point in the steady creep stage; ε i represents the strain corresponding to the t i time.

[0055] An electronic device includes a processor, a memory, a user interface, and a network interface. The memory is used to store instructions. The user interface and the network interface are used to communicate with other devices. The processor is used to execute the instructions stored in the memory so that the electronic device executes a method for constructing a three-dimensional creep constitutive model of sliding zone soil considering hardening-damage effects.

[0056] A computer-readable storage medium stores instructions that, when executed, execute a method for constructing a three-dimensional creep constitutive model of sliding zone soil considering hardening-damage effects.

[0057] The beneficial effects brought by the technical solution provided by this application are:

[0058] The present invention considers the hardening-damage competition mechanism in the whole process of sliding zone creep, respectively introduces a hardening factor and a damage factor into the creep parameters to quantitatively characterize the strengthening and weakening effects of the performance of rock and soil masses during creep, and constructs a creep constitutive model of sliding zone considering hardening-damage effects, which can accurately describe the creep mechanical behavior of structural sliding zone soil. Description of the Drawings

[0059] The following will further illustrate this application in conjunction with the drawings. In the drawings:

[0060] Figure 1It is the step diagram in the embodiment of the present application;

[0061] Figure 2 It is the microscopic schematic diagram of the creep hardening-damage competition mechanism of the original state slip zone soil in the embodiment of the present application;

[0062] Figure 3 It is the framework diagram of the seven-element creep model considering the hardening-damage effect in the embodiment of the present application;

[0063] Figure 4 It is the FLAC in the embodiment of the present application 3D computational schematic diagram;

[0064] Figure 5 It is the secondary development flow chart in the embodiment of the present application;

[0065] Figure 6 It is the schematic diagram of the electronic device structure in the embodiment of the present application. Detailed implementation manners

[0066] For a clearer understanding of the technical features, objectives, and effects of the present application, the detailed implementation manners of the present application will now be described in detail with reference to the accompanying drawings.

[0067] The embodiment of the present application provides a method for constructing a three-dimensional creep constitutive model of slip zone soil considering the hardening-damage effect.

[0068] Please refer to Figure 1 , Figure 1 which is the step diagram of a method for constructing a three-dimensional creep constitutive model of slip zone soil considering the hardening-damage effect in the embodiment of the present application, and includes:

[0069] S1: Obtain the creep test results of the original state slip zone soil;

[0070] As an embodiment, a triaxial compression creep test is carried out on the original state slip zone soil to obtain the stress-time curves of the slip zone soil under different confining pressures and deviator stresses; the creep curve (stress-time curve) of the original state slip zone soil includes three stages: instantaneous creep, attenuation creep, and steady creep.

[0071] S2: Construct the hardening evolution equation and the damage evolution equation;

[0072] S3: Construct a seven-element creep model considering the hardening-damage effect through the hardening evolution equation and the damage evolution equation;

[0073] S4: Based on the constant volume assumption, combine the seven-element creep model to construct a three-dimensional creep constitutive model of slip zone soil considering the hardening-damage effect;

[0074] S5: According to the creep test results of the undisturbed slip zone soil, combined with the method of fitting the test curve in stages, solve the creep parameters of the three-dimensional creep constitutive model of the slip zone soil, and complete the construction of the three-dimensional creep constitutive model of the slip zone soil.

[0075] Step S2 includes:

[0076] The steps of analyzing the hardening-damage competition mechanism in the whole creep process and constructing the hardening evolution equation are as follows:

[0077] Assume that the hardening effect of the undisturbed slip zone soil starts at the instant of loading and ends at the steady creep stage, satisfying that when the time tends to 0, the hardening factor H is 0, and when the time tends to infinity, the hardening factor H is a constant;

[0078] The hardening factor H is a function related to stress and time, then the hardening evolution equation is as follows:

[0079] H = e -λt -1

[0080] In the formula, λ is a parameter reflecting the strengthening degree of the slip zone soil, that is, a stress-related parameter, which is obtained through the creep test results of the undisturbed slip zone soil; t is the creep time.

[0081] Step S3 includes:

[0082] The steps of analyzing the hardening-damage competition mechanism in the whole creep process and constructing the damage evolution equation are as follows:

[0083] Assume that the damage effect of the undisturbed slip zone soil rapidly increases at the end of the decaying creep stage, and the damage effect is used to control the steady creep stage and the accelerating creep stage; assume that the damage factor D is a piecewise function, then the damage evolution equation is as follows:

[0084]

[0085] In the formula, q represents the deviator stress; σ y is the critical stress between the decaying creep stage and the steady creep stage; α is a coefficient reflecting the damage degree of the geotechnical material, which is related to the stress σ; t is the creep time.

[0086] The present application provides an embodiment as follows. Analyze the hardening-damage competition mechanism in the whole creep process and construct the hardening evolution equation and the damage evolution equation; the creep of the slip zone soil is the result of the combined action of hardening and damage, and its micro schematic diagram is as Figure 2As shown in the figure. On the one hand, the pores and cracks in the soil mass are compressed, resulting in the rearrangement of soil particles and the formation of new connections, thereby increasing the cohesion and showing a hardening effect; on the other hand, under the action of external forces, the particles slip, microcracks are generated and expanded, showing a damage effect, thus gradually deteriorating the mechanical properties of the slip zone soil. According to the deformation characteristics of creep in each stage, in the decaying creep stage, the deformation rate steadily decreases, and the strain-time curve shows a convex change, indicating that the hardening effect caused by microcracks and pore compression plays an important role. Due to the interaction between the closure of tiny pores and the expansion of microcracks, the deformation curve shows a linear upward trend in the steady creep stage, and the deformation rate remains constant at the same time. In the accelerating creep stage, the microcracks in the soil mass rapidly expand, resulting in the damage effect becoming the main cause of creep.

[0087] Step S3 further includes:

[0088] Introduce a hardening factor and a damage factor to correct the creep parameters, and form a seven-element creep model including a Hooke body, a hardening Kelvin body and a hardening-damage Bingham body;

[0089] Construct a seven-element creep model considering the hardening-damage effect, specifically as follows:

[0090]

[0091] In the formula, σ represents the stress parameter; E0 represents the elastic modulus of the spring element; E1 represents the elastic modulus of the viscoelastic element; λ1 represents the coefficient related to stress in the hardening factor function introduced by the viscous element in the viscoelastic element; η1 represents the viscosity coefficient; t represents the creep time; σ y represents the critical stress between the decaying creep stage and the steady creep stage, that is, the yield stress; ξ represents the coupling coefficient of damage and hardening; η2 represents the viscosity coefficient; σ s represents the long-term strength.

[0092] The present application provides an embodiment as follows. Considering the complexity of the slip zone deformation mechanism and the convenience of constitutive secondary development, on the basis of the traditional Nishihara model, a hardening factor and a damage factor are introduced in each stage of creep to correct the viscosity coefficient (i.e., the creep parameter), and a seven-element creep model that can comprehensively reflect the creep mechanism of the slip zone soil is proposed. As Figure 3 shown, the constructed creep model of the slip zone soil considering the hardening-damage competition mechanism consists of four parts: the Hooke body, which reflects the elastic strain corresponding to the instantaneous deformation state of the creep curve; the Kelvin body introduced with the hardening factor H1, which is used to characterize the viscoelastic strain in the decaying creep stage; the improved Bigham body introduced with the hardening factor H2 and the damage factor D1, which describes the viscoplastic strain in the steady creep stage. The corresponding state is σ y <σ < σ s, at this time, the creep curve includes the attenuation and steady creep stages; the Bingham body with the damage factor D2 introduced describes the deformation in the accelerated creep stage. The corresponding state is σ > σ s , at this time, the stress exceeds the stress threshold σ s of the accelerated creep stage, and the creep curve includes the attenuation, steady, and accelerated creep stages.

[0093] Step S4 includes:

[0094] The three-dimensional creep constitutive model of the sliding zone soil considering the hardening-damage effect is as follows:

[0095]

[0096] where represents the deviatoric stress tensor, i and j represent different spatial directions. Usually in three-dimensional space, i, j ∈ {1, 2, 3}, corresponding to the x, y, and z directions respectively; σ m represents the spherical stress tensor; δ ij represents the Kronecker symbol; ε ij represents the total strain; and represent the strains of the Hooke body, the hardened Kelvin body, and the Bingham body with the coupling effect of hardening and damage respectively; δ ij is the Kronecker function; G0 represents the shear modulus of the spring element; K represents the bulk modulus of the spring element; G1 represents the shear modulus of the viscoelastic element; H1 represents the hardening factor introduced by the viscoelastic element; represents the switching function; F represents the switching function; F0 represents the initial value of the yield function; Q is the plastic potential function. When F ≥ 0, Q = F; H2 represents the hardening factor introduced by the viscoplastic element; D1 represents the damage factor introduced by the viscoplastic element; σ ij represents the stress tensor;

[0097]

[0098] In the formula, x represents the exponent of the power function. For soil materials, F0 = 1 and x = 1; J2 represents the second invariant of the stress tensor; σ y represents the critical stress between the attenuation creep stage and the steady creep stage; σ1 represents the maximum principal stress; σ3 represents the maximum principal stress.

[0099] Step S5 includes:

[0100] According to the creep test results of the undisturbed sliding zone soil, determine the creep parameters of the three-dimensional creep constitutive model of the sliding zone soil; the creep parameters include: G0, G1, λ1, η1, σ y , ξ and η2;

[0101] Based on the characteristic points of the test curve, the creep parameters are solved by the method of fitting the test curve in stages. The specific steps are as follows:

[0102] S51: Through the triaxial creep test, the initial strain ε1 under different deviator stress levels is obtained. According to Equation (5), the shear modulus G0 and bulk modulus K under different confining pressures are determined.

[0103] S52: When the deformation of the sliding zone soil sample enters the decaying creep stage from the instantaneous strain stage and the creep time approaches infinity, the following relationship exists:

[0104]

[0105] where ε HK is the sum of the Hooke body strain and the hardened Kelvin body strain;

[0106] By fitting the data (t, F(t)), the values of the shear modulus G1, viscosity coefficient η1, and coefficient λ1 are obtained.

[0107] S53: The solution steps for the yield stress σ y , viscosity coefficient η2, and coefficient ξ are as follows:

[0108] When the sliding zone soil enters the steady creep stage from the decaying creep stage, the creep rate is a constant value, which is expressed as the first derivative of creep with respect to time, specifically as follows:

[0109]

[0110] The yield stress σ y is the critical value between the decaying stage and the steady stage, that is, the first inflection point of the creep curve, and the creep curve is obtained from the creep test results of the undisturbed sliding zone soil.

[0111] To solve the viscosity coefficient η2 and coefficient ξ, specifically including: taking n points (t i , ε i ) in the steady creep stage, where the value range of i is (1, n), and the following is obtained:

[0112]

[0113] where ξ i represents the ξ value at a certain t i time in the steady creep stage; t i represents a certain time point in the steady creep stage; ε i represents the strain corresponding to the t i time.

[0114] This embodiment provides a numerical application method for a creep constitutive model considering the hardening-damage competition effect. The FLAC3D software numerically simulates three-dimensional geological problems through the finite difference method. Its calculation process includes updating stress and strain based on difference equations, checking for yielding through the Mohr-Coulomb yield criterion, and correcting stress when yielding occurs. In addition, the model is developed using Microsoft Visual Studio and FLAC3D, and through numerical verification and comparison with experimental data, its reliability and applicability under different loading conditions are ensured.

[0115] The present invention derives the three-dimensional difference form of the creep constitutive model of the slip zone, and further obtains an application program through programming. The finite difference software calls the said application program, providing an important theoretical basis and numerical tool for the deformation prediction of large-scale accumulation layer landslides.

[0116] The secondary development and application process of the creep model are shown in Figure 4 , which mainly includes transforming the stress-strain relationship in the creep constitutive model into a difference equation, deriving the stress correction equation, secondary development of the creep model, and verification of the developed model. The specific steps are as follows:

[0117] Step 1: According to the calculation principle of FLAC3D and in combination with the constructed three-dimensional creep constitutive model of the slip zone soil, derive the three-dimensional difference form of the three-dimensional creep constitutive model of the slip zone soil;

[0118] Specifically as follows:

[0119]

[0120] Among them, Δe ij is the total deviatoric strain tensor increment of the Nishihara model considering damage and hardening effects, are respectively the deviatoric strain tensor increments of the Hooke body, the hardened Kelvin body, and the hardening-damage coupled Bingham body; ΔS ij represents the deviatoric stress increment; G0 represents the shear modulus of the spring element; Δt represents the time increment; η2 represents the viscosity coefficient of the viscoplastic element; ξ represents the damage and hardening coupling coefficient; represents the switching function, F represents the yield function, F0 represents the initial value of the yield function; Q is the plastic potential function; σ ij represents the stress tensor; represents the plastic volumetric strain increment; δ ij is the Kronecker symbol; and respectively represent the new deviatoric stress and the old deviatoric stress within a time step; represents the deviatoric strain tensor of the old hardened Kelvin body within a time step; a, b, A, and B are all coefficients; G1 is the shear modulus of the viscoelastic element; η1 is the viscosity coefficient of the viscoelastic element; λ1 is the coefficient of the hardening factor introduced by the viscoelastic element.

[0121] Step 2: Select a yield criterion to correct the stress-strain of the three-dimensional creep constitutive model of the sliding zone soil. In FLAC 3D During the solution process, when the material undergoes plastic deformation, a stress correction equation needs to be used to adjust its stress state. FLAC 3D The stress correction equation in it is mainly based on the yield criterion of the material. The present invention introduces the Mohr-Coulomb yield criterion to judge whether the material yields. When the stress exceeds a certain yield value, the model needs to adjust the stress to meet the requirements of plastic deformation. In FLAC 3D In, the yield criterion is generally judged by comparing the shear stress and normal stress of the material with its shear strength and tensile strength.

[0122] In FLAC 3D During the solution process, when the material undergoes plastic deformation, a stress correction equation needs to be used to adjust its stress state. FLAC 3D The stress correction equation in it is mainly based on the yield criterion of the material. The present invention introduces the Mohr-Coulomb yield criterion to judge whether the material yields. When the stress exceeds a certain yield value, the model needs to adjust the stress to meet the requirements of plastic deformation. In FLAC 3D In, the yield criterion is generally judged by comparing the shear stress and normal stress of the material with its shear strength and tensile strength, as follows:

[0123]

[0124] g s = σ1 - σ3N ψ

[0125] f t = σ t - σ3

[0126] g t = σ1 - σ3N ψ

[0127] where f s and g s are the yield function and potential function of shear failure respectively, f t and g t are the yield function and potential function of tensile failure respectively, σ1 is the maximum principal stress, σ3 is the minimum principal stress, φ is the friction angle, C is the cohesion, ψ is the dilation angle, is the tensile strength.

[0128] When the calculated stress exceeds the yield stress, the stress needs to be adjusted by the stress correction equation. The stress correction formula is as follows:

[0129]

[0130] where and are the corrected principal stress and the initial principal stress obtained from the trial stress respectively, and i = 1, 2, 3 correspond to the maximum principal stress, the intermediate principal stress, and the minimum principal stress respectively; are the plastic strain increments corresponding to the three principal stresses respectively; α1 and α2 are coefficients, K is the bulk modulus.

[0131] Furthermore, when the element is in shear yield, the updated principal stress and plastic strain are as follows:

[0132]

[0133]

[0134] where γ is a coefficient, Δt is the time increment; η2 is the viscosity coefficient of the viscoplastic element; ξ represents the damage and hardening coupling coefficient; φ is the friction angle, C is the cohesion, and ψ is the dilatancy angle.

[0135] Furthermore, when the element is in tensile yield, the updated principal stress and plastic strain are as follows:

[0136]

[0137] where and are the corrected principal stress and the initial principal stress obtained from the trial stress (i = 1, 2, 3 correspond to the maximum principal stress, the intermediate principal stress, and the minimum principal stress respectively); β is a coefficient; is the initial value of the tensile strength; Δt is the time increment; η2 is the viscosity coefficient of the viscoplastic element; ξ represents the damage and hardening coupling coefficient.

[0138] Step 3: Based on Microsoft Visual Studio 2015 and FLAC 3D 6.0, the constructed creep model is redeveloped. The redevelopment process is shown in Figure 5 , including the setting of the redevelopment environment, modifying the.h file and.cpp file, embedding and calling the redeveloped model, and simulation verification.

[0139] Step 3-1: Setting up the secondary development environment of Microsoft Visual Studio 2015 software. The creep model constructed in the present invention takes into account damage and hardening effects and belongs to a non-linear visco-elasto-plastic model. In the plastic part, the Mohr-Coulomb criterion is introduced for modification. Therefore, for the convenience of modification, it is reasonable to select the Cvisc model from the creep constitutive models built into FLAC 3D as the basis for developing a custom model. Compared with the Cvisc model, the constructed creep model lacks a viscous element in the Maxwell part and takes into account damage and hardening effects. During calculation, the viscosity coefficient in the Maxwell element can be assigned a value of zero, and damage and hardening factors can be introduced into the viscous element of the model for processing to implement the programming of the custom model. Run Visual Studio 2015, select FLAC600 Constitutive Model in the Visual C++ template to create a new project with the model name Hdx, generating a solution based on the Mohr-Coloumb model template. In the newly created Solution Explorer, the header files (.h), source files (.cpp), and external dependencies required for managing and editing the custom model can be managed. Among them, the Header Files contain header files with the suffix.h, the Resource Files contain source files with the suffix.rc, the Source Files contain source files with the suffix.cpp, the ReadMe.txt file is a description file, and the version.txt file is a version information file.

[0140] Step 3-2: Modify the header file (.h) and source file (.cpp). During the modification of the header file (modelhdx.h) of the custom constitutive model, first ensure that the header file is only compiled once to avoid naming conflicts and the redundancy issues of multiple compilations. This header file includes the base class functions of the model, the common parts, and the declarations of private variables. By compilation, the custom model is connected to the base class, supporting the overloading of real functions. In the header file, the key parts include the declarations of derived classes and the implementation of virtual functions, such as getName(), getFullName(), getProperties(), etc., which are used to obtain the name, version, properties, etc. of the model. In addition, the name of the model and the names of material parameters are also declared to ensure correct reference during calls. The private variable part includes various parameters in the creep equation, such as Bulk, Kshear, Mshear, Kviscosity, etc., covering the physical quantities related to creep in the model, as well as the key variables in the theoretical model, such as the strain increment Mekd[6], etc. The core part of the modification of the source file (.cpp) includes five functional modules: declaration part, model registration, parameter and state definition, parameter call and replication, initialization and iteration. First, the source file introduces multiple library files, providing support for model structure, state functions, numerical conversion, version information, etc. In the model registration part, macros and stub functions are defined to handle dynamic library loading, unloading, and the creation of model instances. The parameter and state definition part involves the acquisition of model parameters, property definition, and the output format of model states, especially the introduction of hardening and damage parameters λ and α. In the parameter call and replication part, the setProperty() function is used to assign the parameter values input by the user to the model variables, and the copy() function is used to copy model data to ensure avoiding duplicate calculations. The initialization and iteration part is crucial. The initialize() function sets the initial state for the model, and the run() function is responsible for iteratively updating variables and performing calculations, especially for elastic calculations before material yielding and synchronously updating plastic strain and viscoelastic strain after yielding. The implementation of the creep process is completed through FISH language, and the hardening and damage factors are updated in each creep step until the creep calculation is completed. This process controls the step size through a loop function, synchronously with the creep time.

[0141] Step 3-4: Embedding and calling the secondary development model. After editing modelhdx.h and modelhdx.cpp, attempt to regenerate the solution in the Release and x64 system environments. The cmodelhdx006_64.dll file is successfully generated in the folder and displayed in the output window. The generated.dll file is stored in the solution folder created by Visual Studio. It needs to be copied to the exe64 folder in the installation directory of FLAC3D 6.0 to achieve the call in the software. In FLAC 3D In the software, input the command "model configure plugin" through the FISH language to call the generated.dll file of the custom constitutive model.

[0142] Step 3-5: Simulation verification. Based on the Rhnio-Griddle software, construct a three-dimensional grid model of the slip zone / landslide and import it into the FLAC3D software. Call the.dll file of the constructed creep model to simulate and analyze the creep hardening-damage behavior of the slip zone / landslide. Compare the simulation results with the test and monitoring data to verify the correctness and applicability of the secondary development creep model, providing an important theoretical model and numerical tool for revealing the deformation and evolution mechanism of the landslide.

[0143] This application also discloses an electronic device. Refer to Figure 6 , Figure 6 which is a schematic structural diagram of an electronic device disclosed in an embodiment of this application. The electronic device 500 may include: at least one processor 501, at least one network interface 504, a user interface 503, a memory 505, and at least one communication bus 502.

[0144] Among them, the communication bus 502 is used to realize the connection and communication between these components.

[0145] Among them, the user interface 503 may include a display screen. Optionally, the user interface 503 may further include a standard wired interface and a wireless interface.

[0146] Among them, the network interface 504 may optionally include a standard wired interface and a wireless interface (such as a WI-FI interface).

[0147] This application also discloses a computer-readable storage medium that stores multiple instructions suitable for a processor to load and execute the above-mentioned method for constructing a three-dimensional creep constitutive model of slip zone soil considering hardening-damage effects.

[0148] The above are only exemplary embodiments of the present disclosure, and the scope of the present disclosure cannot be limited thereby. That is, any equivalent changes and modifications made in accordance with the teachings of the present disclosure still fall within the scope covered by the present disclosure.

[0149] This application is intended to cover any variations, uses, or adaptations of the present disclosure, which follow the general principles of the present disclosure and include common general knowledge or conventional technical means in the technical field not recorded in the present disclosure. The description and examples are only considered exemplary, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A construction method for a three-dimensional creep constitutive model of landslide soil considering hardening-damage effects, characterized in that, The method includes the following steps: S1: Obtain the creep test results of undisturbed slip zone soil; S2: Construct a hardening evolution equation and a damage evolution equation; S3: Through the hardening evolution equation and the damage evolution equation, construct a seven-element creep model considering the hardening-damage effect; S4: Based on the constant volume assumption, combined with the seven-element creep model, construct a three-dimensional creep constitutive model of slip zone soil considering the hardening-damage effect; S5: According to the creep test results of undisturbed slip zone soil, combined with the method of fitting test curves in stages, solve the creep parameters of the three-dimensional creep constitutive model of slip zone soil, and complete the construction of the three-dimensional creep constitutive model of slip zone soil.

2. The construction method of a three-dimensional creep constitutive model for landslide soil considering hardening-damage effect according to claim 1, characterized in that Step S2 includes: Analyze the hardening-damage competition mechanism in the whole process of creep. The steps to construct the hardening evolution equation are as follows: Assume that the hardening effect of undisturbed slip zone soil starts at the instant of loading and ends at the stage of steady creep, satisfying that when the time tends to 0, the hardening factor H is 0, and when the time tends to infinity, the hardening factor H is a constant; Since the hardening factor H is a function related to stress and time, the hardening evolution equation is as follows: H = e -λt-1 (1) In the formula, λ is a parameter reflecting the strengthening degree of slip zone soil, that is, a stress-related parameter, which is obtained through the creep test results of undisturbed slip zone soil; t is the creep time.

3. The construction method of a three-dimensional creep constitutive model for landslide soil considering hardening-damage effect as claimed in claim 1, wherein Step S3 includes: Analyze the hardening-damage competition mechanism in the whole process of creep. The steps to construct the damage evolution equation are as follows: Assume that the damage effect of undisturbed slip zone soil rapidly increases at the end of the attenuation creep stage, and the damage effect is used to control the steady creep stage and the accelerating creep stage; assume that the damage factor D is a piecewise function, then the damage evolution equation is as follows: where q represents the deviatoric stress; σ y is the critical stress between the attenuation creep stage and the steady creep stage; α is a coefficient reflecting the damage degree of geotechnical materials, which is related to the stress σ; t is the creep time.

4. The construction method of a three-dimensional creep constitutive model for landslide soil considering hardening-damage effect as described in claim 1, characterized in that, Step S3 also includes: Introduce the hardening factor and the damage factor to correct the creep parameters, and form a seven-element creep model including a Hooke body, a hardened Kelvin body and a hardened-damaged Bingham body; Construct a seven-element creep model considering the hardening-damage effect, specifically as follows: In the formula, σ represents the stress parameter; E0 represents the elastic modulus of the spring element; E1 represents the elastic modulus of the viscoelastic element; λ1 represents the stress-related coefficient in the hardening factor function introduced by the viscous element in the viscoelastic element; η1 represents the viscosity coefficient; t represents the creep time; σ y represents the critical stress between the attenuation creep stage and the steady creep stage, that is, the yield stress; ξ represents the damage and hardening coupling coefficient; η2 represents the viscosity coefficient; σ s represents the long-term strength.

5. The construction method of a three-dimensional creep constitutive model for landslide soil considering hardening-damage effect as claimed in claim 4, characterized in that, Step S4 includes: The three-dimensional creep constitutive model of slip zone soil considering the hardening-damage effect is specifically as follows: where represents the deviatoric stress tensor, i and j represent different spatial directions. Usually in a three-dimensional space, i, j ∈ {1, 2, 3}, corresponding to the x, y, and z directions respectively; σ m represents the spherical stress tensor; δ ij represents the Kronecker symbol; ε ij represents the total strain; and represent the strains of the Hooke body, the hardened Kelvin body, and the Bingham body with the coupling effect of hardening and damage respectively; δ ij is the Kronecker function; G0 represents the shear modulus of the spring element; K represents the bulk modulus of the spring element; G1 represents the shear modulus of the viscoelastic element; H1 represents the hardening factor introduced by the viscoelastic element; represents the switching function; F represents the switching function; F0 represents the initial value of the yield function; Q is the plastic potential function, when F ≥ 0, Q = F; H2 represents the hardening factor introduced by the viscoplastic element; D1 represents the damage factor introduced by the viscoplastic element; σ ij represents the stress tensor; In the formula, x represents the exponent of the power function. For soil material, F0 = 1 and x = 1; J2 represents the second invariant of the stress tensor; σ y represents the critical stress between the attenuation creep stage and the steady creep stage; σ1 represents the maximum principal stress; σ3 represents the minimum principal stress.

6. The construction method of a three-dimensional creep constitutive model for landslide soil considering hardening-damage effect as claimed in claim 5, characterized in that Step S5 includes: According to the creep test results of the undisturbed sliding zone soil, determine the creep parameters of the three-dimensional creep constitutive model of the sliding zone soil; the creep parameters include: G0, G1, λ1, η1, σ y , ξ and η2; Based on the characteristic points of the test curve, solve the creep parameters through the method of fitting test curves in stages. The specific steps are as follows: S51: Through the triaxial creep test, obtain the initial strain ε1 under different deviator stress levels, and according to Equation (5), determine the shear modulus G0 and the bulk modulus K under different confining pressures; S52: When the deformation of the slip zone soil sample enters the attenuation creep stage from the instantaneous strain stage, when the creep time tends to infinity, there is the following relationship: where ε HK is the sum of the Hooke body strain and the hardened Kelvin body strain; By fitting the data (t, F(t)), obtain the values of the shear modulus G1, the viscosity coefficient η1 and the coefficient λ1; S53: Yield stress σ y , the solution steps for the viscosity coefficient η2 and the coefficient ξ are as follows: When the slip zone soil enters the steady creep stage from the attenuation creep stage, the creep rate is a constant value, which is expressed as the first derivative of creep with respect to time, specifically as follows: Yield stress σ y is the critical value between the attenuation stage and the stable stage, that is, the first inflection point of the creep curve, which is obtained from the creep test results of the undisturbed slip zone soil; Solve for the viscosity coefficient η2 and the coefficient ξ, specifically including: taking n points (t i , ε i ) in the steady creep stage, where the value range of i is (1, n), and obtaining: where ξ i represents the value of ξ at a certain t i during the steady creep stage; t i represents a certain time point during the steady creep stage; ε i represents the strain corresponding to t i at that time.

7. An electronic device, characterized in that, It includes a processor, a memory, a user interface and a network interface. The memory is used to store instructions. The user interface and the network interface are used to communicate with other devices. The processor is used to execute the instructions stored in the memory, so that the electronic device executes the method described in any one of claims 1-6.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions that, when executed by a computer, perform the method according to any one of claims 1-6.

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