A discrete element numerical simulation method for contact creep deformation of rock and soil particles

Abstract

The present application is a kind of geotechnical particle contact creep deformation discrete element numerical simulation method, the method is used to simulate long time contact creep between coarse particles, respectively determine four parameters in burgers model of normal coarse particle contact creep and tangential coarse particle contact creep;Obtain the corresponding four parameters under all different normal loads, the corresponding four parameters under all different normal loads and different tangential loads, respectively function fitting with load as independent variable and parameter as dependent variable, respectively obtain the function expression of eight parameters and load, and embed burgers model in PFC3D software;When the input normal load and tangential load are determined, the parameters in burgers model can be dynamically adjusted, and then the particle contact creep displacement under any load condition and time can be obtained. Break through the limitation of laboratory test, realize the quantitative prediction of rheological deformation of coarse aggregate in actual engineering.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, specifically a discrete element numerical simulation method for contact creep deformation of soil particles. Background Technology

[0002] Currently, dam construction in the engineering field mainly focuses on earth-rock dams and rockfill dams. These dams use coarse-grained soil as fill material. However, in the later stages of actual operation, earth-rock dams experience unexpected settlement, and this deformation usually lasts for a long time. A major reason for the long-term deformation of the dam body is the long-term deformation of its main structural fill material, namely, the coarse-grained soil and rock.

[0003] For coarse-grained riprap and other non-cohesive soils, their macroscopic mechanical properties are mainly influenced by factors such as particle connectivity and arrangement at the microscopic level. In recent years, scholars have begun to delve deeper into the study of particle contact mechanics to more comprehensively explain the macroscopic mechanical phenomena of coarse-grained soils from a microscopic perspective. This type of research holds promise for exploring the macroscopic physical laws governing coarse-grained soils. It is worth noting that this is still in its early stages, with limited research results, but this field has extremely high potential value. The above research on particle contact mechanics focuses on spherical and cubic particles, simplifying particle contact to point-to-point contact and exploring contact mechanics through particle contact experiments. However, there are currently no research results on particle contact creep in this field.

[0004] PFC3D (Particle Flow Code in Three Dimensions), a discrete element method software, is a numerical simulation software specifically designed for studying the properties of granular materials. It is well-suited for particle contact experiments, and provides the Burgers model for contact creep of non-cohesive granular materials. The Burgers model, a combination of Maxwell and Kelvin models, combines the advantages of both and can effectively describe each creep stage of particle contact. However, during calculations, the Burgers model requires parameter determination. Current technology often uses parameter fitting methods, inputting fixed parameter values, which lacks scientific rigor. For example, in CN202010075697.4, to simplify calculations, the parameters of the four discrete element nonlinear contact rheological models of the Kelvin volume model in the Burgers model were made infinitely large, ignoring the Kelvin volume in the Burgers model. This simplifies the original 10 parameters of the Burgers model to 6, resulting in what is essentially using the Maxwell model directly to describe coarse particle contact creep, leading to low accuracy. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a discrete element numerical simulation method for particle contact creep deformation in soil and rock. This method determines 10 parameters of the Burgers model based on normal particle contact creep tests and tangential particle contact creep tests, and can accurately simulate the deformation amount of particle contact deformation in particle contact tests.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A discrete element numerical simulation method for contact creep deformation of soil particles, the method being used to simulate long-term contact creep between coarse particles, includes the following steps:

[0008] The Burgers models for normal coarse-grained contact creep and tangential coarse-grained contact creep are given by equations (1) and (6), respectively.

[0009]

[0010]

[0011] Among them, U n F represents the normal displacement of the soil particles. n It is the normal load on the specimen, k n2 η n2 These are the normal spring stiffness and normal viscosity coefficient of a Maxwell body, k n1 η n1 These are the normal spring stiffness and normal viscosity coefficient of a Kelvin body; subscript n represents the normal direction; subscript s represents the tangential direction; t is time; U s F represents the tangential displacement of the soil particles. s It is the tangential load on the specimen, k s2 η s2 These are the tangential spring stiffness and tangential viscosity of a Maxwell body, k s1 η s1 These are the tangential spring stiffness and tangential viscosity of the Kelvin body;

[0012] Determine the four parameters for each of the two burger models;

[0013] The first step is to conduct normal particle contact creep tests to obtain the normal time-displacement curves of coarse particles under different normal loading conditions; a single normal particle contact creep test can determine a set of k... n2 η n2 k n1 η n1 These four values ​​are all related to the normal load F in this test. n Corresponding to the conditions;

[0014] Under normal load F n Given the conditions, record the instantaneous displacement U corresponding to time t=0 during the normal particle contact creep test. n | t＝0 According to U n | t＝0 and F n Substitute the value into U n | t＝0 =F n / k n2 Obtain the parameter k under the current normal load. n2 The value;

[0015] In determining parameter k n2 After obtaining the value, the time and normal displacement data under the normal load are obtained. Based on formula (1), function fitting is performed using Oringin software. After fitting, the normal load and the corresponding k are substituted into the data. n2 Then, based on the coefficient term of time t, η can be solved inversely. n2 k n1 η n1 ;

[0016] Obtain the four parameters corresponding to all different normal loads, respectively, with the normal load F n With one variable as the independent variable and four parameters as the dependent variable, a function is fitted to obtain the normal constitutive parameters k. n2 η n2 k n1 η n1 With normal load F n The functional expression of the relation;

[0017] The second step is to conduct a tangential particle contact creep test. In this test, a normal load is applied first, and then a tangential force is applied after stabilization. A single tangential particle contact creep test can determine a set of k values. s2 η s2 k s1 η ns1 These four values ​​are all related to the normal load F in this test. n and tangential load F s Corresponding to;

[0018] Under tangential load F s Given the conditions, record the instantaneous displacement U corresponding to time t=0 during the tangential particle contact creep test. s | t＝0 According to U s | t＝0 and F s Substitute the value into U s | t＝0 =F s / ks2 Obtain the parameter k under the current tangential load. n2 The value;

[0019] In determining parameter k s2 After obtaining the values, the data of time and tangential displacement under normal and tangential loads are obtained. Based on formula (6), function fitting is performed using Oringin software. After fitting, the tangential load and the corresponding k are substituted into the data. s2 Then, based on the coefficient term of time t, η can be solved inversely. s2 k s1 η s1 ;

[0020] Obtain the four parameters corresponding to all different normal loads and different tangential loads, with the normal load F as the parameter. n As the independent variable, with k s2 Perform function fitting on the dependent variable to obtain k s2 With normal load F n The functional expression; with normal load F n and tangential load F s As the independent variable, with k s1 Perform function fitting on the dependent variable to obtain k s1 With normal load F n Tangential load F s The functional expression; with tangential load F s Let η be the independent variable. s2 η s1 Perform function fitting on the dependent variable to obtain η. s2 η s1 Respectively with tangential load F s The function expression;

[0021] The third step is to embed the functional expressions of the eight parameters and loads into the burgers model in PFC3D software, and change each parameter of the burgers model in PFC3D software to the above functional expressions.

[0022] Once the input normal and tangential loads are determined, the parameters in the Burgers model can be dynamically adjusted, thereby obtaining the particle contact creep displacement under arbitrary load conditions and time.

[0023] For the test specimens, normal particle contact creep test and tangential particle contact creep test were performed under different degrees of humidification.

[0024] Obtain the normal constitutive parameter k under different humidification degrees. n2 η n2 k n1 η n1 With normal load Fn The functional expression of the relation, and the tangential constitutive parameter k s2 With normal load F n The functional expression of the relation, k s1 With normal load F n Tangential load F s The function expression of η; s2 η s1 Respectively with tangential load F s The function expression;

[0025] Based on the functional expression under natural moisture content conditions, the multiple relationship between different humidification degrees and natural conditions is determined, and this multiple relationship is denoted as the humidification coefficient.

[0026] By adding a humidification coefficient input port to the PFC3D software, the parameters of the burgers model can be dynamically adjusted according to the input load and working conditions, thus obtaining particle contact creep displacement under arbitrary load conditions, working conditions and time.

[0027] In PFC3D software, the burgers model includes ten parameters:

[0028] Kelvin body normal spring stiffness k n1 The corresponding software is bur_knk

[0029] The normal spring stiffness k of a Maxwell body n2 The corresponding software is bur_cnk

[0030] The normal viscosity coefficient η of Kelvin's body n1 The corresponding bur_knm in the software

[0031] The normal viscosity η of Maxwell volume n2 The corresponding bur_knm in the software

[0032] Kelvin body tangential spring stiffness k s1 The corresponding software is bur_ksk

[0033] tangential spring stiffness k of a Maxwell body s2 The corresponding software is bur_csk

[0034] The tangential viscosity η of Kelvin's body s1 The corresponding software is bur_ksm

[0035] Maxwell volume tangential viscosity η s2 The corresponding software is bur_csm

[0036] The function expressions for the above eight parameters were recorded using the fish language and input into the burgers model of the PFC software to calculate the deformation of the particle contact test.

[0037] The coefficient of friction, fric, takes extreme values.

[0038] Set the tension switch bur_notension to 1.

[0039] The test subjects were cubic and conical soil particles with a diameter of 5 cm, which were subjected to point-to-surface contact.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] This invention focuses on the contact creep study of cohesive soils and granular particles, where no tensile force is applied between particles. Contact creep tests were conducted on coarse particles under normal and tangential loading conditions. The Burgers model was used to describe and fit the creep curves. Parameters were obtained through creep tests (the relationship between normal parameters and normal stress, and the relationship between tangential parameters and normal and tangential stresses). The Burgers model in PFC3D software was further developed using the FIS language, modifying each parameter into a corresponding functional relationship. Furthermore, the relationship between the degree of wetting and the parameters under natural moisture content conditions was obtained, enabling the Burgers model parameters to dynamically adjust during calculation based on the input load and working conditions (natural moisture content can be represented by 1, and different numbers can represent different working conditions), rather than being a fixed value. This allows for the calculation of particle contact creep displacement under arbitrary load conditions and time.

[0042] Compared with the inventor's prior application CN202010075697.4, which describes the construction method and application of the Burger model, this invention simplifies calculations by making the four discrete-element nonlinear contact rheological model parameters of the Kelvin volume model in the Burger model infinitely large, neglecting the Kelvin volume in the Burger model. In other words, it simplifies the original 10 parameters of the Burger model to 6. This results in the direct use of the Maxwell model to describe coarse-grained contact creep. Strictly speaking, this patent is not a method for determining and applying the parameters of the Burger model, but rather a method for determining and applying the parameters of the Maxwell model. In contrast, this patent, through extensive and comprehensive experiments, strictly follows the 10 parameters given by the Burger model in the PFC numerical calculation theory to simulate coarse-grained contact creep experiments. It uses the discrete-element software PFC3D to establish a numerical model of particle contact for numerical simulation, studying the mechanical properties under different stress states. Therefore, this application breaks through the limitations of indoor testing and realizes the quantitative prediction of the rheological deformation of coarse-grained materials in actual engineering. The PFC3D discrete element software is used to calculate the deformation of contact creep of coarse-grained materials. Attached Figure Description

[0043] Figure 1 A schematic diagram of the burger model.

[0044] Figure 2 A schematic diagram of the burgers model in PFC.

[0045] Figure 3 Schematic diagram of normal particle contact creep test.

[0046] Figure 4 Schematic diagram of tangential particle contact creep test.

[0047] Figure 5 A schematic diagram of the particle contact time-displacement curve obtained during the specific implementation of this invention.

[0048] Figure 6 Comparison of normal particle contact creep test curves and numerical simulation curves.

[0049] Figure 7 Comparison of tangential particle contact creep test curves and numerical simulation curves. Detailed Implementation

[0050] The present invention will be further explained below with reference to the embodiments and accompanying drawings, but this is not intended to limit the scope of protection of this application.

[0051] This invention provides a discrete element numerical simulation method for particle contact creep deformation in soil and rock, which is proposed for simulating long-term contact creep between coarse particles.

[0052] A schematic diagram of the burger model components is shown below. Figure 1 As shown, the 10 parameters of the Burgers model in the PFC numerical calculation software are:

[0053] 1. The normal spring stiffness k of a Kelvin body n1 The corresponding software is bur_knk

[0054] 2. Normal spring stiffness k of a Maxwell body n2 The corresponding software is bur_cnk

[0055] 3. Normal viscosity coefficient η of Kelvin volume n1 The corresponding bur_knm in the software

[0056] 4. Normal viscosity coefficient η of Maxwell volume n2 The corresponding bur_knm in the software

[0057] 5. Tangential spring stiffness k of the Kelvin body s1 The corresponding software is bur_ksk

[0058] 6. Tangential spring stiffness k of a Maxwell body s2 The corresponding software is bur_csk

[0059] 7. The tangential viscosity coefficient η of Kelvin volume s1 The corresponding software is bur_ksm

[0060] 8. The tangential viscosity coefficient η of Maxwell volume s2 The corresponding software is bur_csm

[0061] 9. Coefficient of friction bur_fric

[0062] 10. Pull switch bur_notension.

[0063] The methods for determining the parameters of the burgers model include:

[0064] To make the coefficient of friction reach its extreme value of 1.0;

[0065] For non-cohesive soils, there is no tensile force between the particles, so set the tension switch to 1;

[0066] The process of determining the parameters of the four discrete-element nonlinear contact rheological models of the normal Kelvin volume and Maxwell volume models in the Burgers model is as follows;

[0067] First, the Burgers formula, applicable to normal coarse-grained contact creep, is given.

[0068]

[0069] Where t is time; U n F represents the normal displacement of the soil particles. n It is the normal load on the specimen, k n2 η n2 These are the normal spring stiffness and normal viscosity coefficient of a Maxwell body, k n1 η n1 These are the normal spring stiffness and normal viscosity coefficient of the Kelvin body. The subscript n represents the normal direction.

[0070] The following is k n2 η n2 k n1 η n1 Expression determination method.

[0071] First, a normal particle contact creep test needs to be conducted to obtain the normal time-displacement curves of coarse particles under normal load conditions of 3kN, 6kN, 9kN, and 12kN. The test objects are cubic and conical soil particles with a particle size of 5cm, and the contact is carried out in a point-to-surface manner.

[0072] Table 1 Grouping of Normal Particle Contact Creep Test

[0073]

[0074] Before proceeding, it should be clarified that a single normal particle contact creep test can determine a set of k values. n2 η n2 k n1 η n1 All four values ​​are related to the load condition F in this test. n Corresponding to.

[0075] In a certain normal contact creep test, parameter k n2 Determination of: normal load F n Taking 3kN as an example, it can be seen from equation (1) that when t=0, U n | t＝0 =F n / k n2 According to the physical meaning, U n | t＝0 It is an instantaneous displacement, U, derived from experiments.n | t＝0 =0.778mm, F n This is the normal load applied to the current group of tests, where F is... n =3kN, change U n | t＝0 and F n Substitute the value into U n | t＝0 =F n / k n2 F can be obtained n =3kN condition k n2 The value is 3.85 kN / mm.

[0076] In a certain normal contact creep test, the parameter η n2 k n1 η n1 Determination of: normal load F n Taking 3kN as an example, when determining the parameter k n2 After obtaining the value, the normal load F is obtained. n The time and normal displacement data at 3kN were used to fit the function of Oringin software to Equation (1), obtaining the fitted time and normal displacement curves, and F was then used to fit the time and normal displacement data. n =3kN and k n2 Substitute 3.85 kN / mm into the equation, and then solve for η using the coefficient term of time t. n2 k n1 η n1 Oringin software automatically calculates the parameter η in this test based on the time-displacement curve data determined by the normal particle contact creep test. n2 = 37734.09 kN·h / mm, k n1 =26.44kN / mm, η n1 = 364.15 kN·h / mm.

[0077] Repeat the above process to obtain the k values ​​corresponding to all load conditions of all other normal contact creep tests in Table 1. n2 η n2 k n1 η n1 The values ​​are listed in Table 2.

[0078] Table 2 Calculation parameters for the normal burgers model

[0079]

[0080] Observe the data and summarize k n2 The variation law under different load conditions is fitted to k. n2The function expression, with F as the independent variable. n The other three parameters η n2 k n1 η n1 Similarly, observe the data separately and fit them to obtain η. n2 k n1 η n1 The function expression, with F as the independent variable. n .

[0081] Normal constitutive parameter k n2 η n2 k n1 η n1 With normal load F n The expression for the relation is:

[0082] k n1 =40.9·F n -0.389 (2)

[0083] η n1 =790·F n -0.718 (3)

[0084] k n2 =0.09·F n +3.5 (4)

[0085] η n2 =F n / 0.000489 (5)

[0086] The process of determining the parameters of the four discrete-element nonlinear contact rheological models for the tangential Kelvin and Maxwell volumes in the Burgers model is as follows: First, the Burgers formula applicable to tangential coarse-grained contact creep is given.

[0087]

[0088] Where t is time; U s F represents the tangential displacement of the soil particles. s It is the tangential load on the specimen, k s2 η s2 These are the tangential spring stiffness and tangential viscosity of a Maxwell body, k s1 η s1 These are the tangential spring stiffness and tangential viscosity of the Kelvin body. The subscript 's' indicates tangential.

[0089] The following is k s2 η s2 k s1 η s1Expression determination method.

[0090] First, a tangential particle contact creep test needs to be conducted. In the tangential particle contact creep test, normal loading should be applied first, and then tangential force should be applied after stabilization. The test groups are shown in Table 3.

[0091] Table 3 Grouping of Tangential Particle Contact Creep Test

[0092]

[0093] Before proceeding, it's important to clarify that a single particle contact creep test can determine a set of k values. s2 η s2 k s1 η s1 These four values ​​are all related to the normal load F in this test. n and tangential load F s Corresponding to.

[0094] In a certain tangential contact creep test, parameter k s2 Determination of F n =3kN, F s Taking the 1kN group test as an example, it can be seen from equation (6) that when t=0, U s | t＝0 =F s / k s2 According to the physical meaning, U s | t＝0 U is the instantaneous displacement generated by the sample, which is obtained from the experiment. n | t＝0 =2.319mm, F s This is the tangential load experienced by the current test group, at which point F s =1kN, U s | t＝0 and F s Substitute the value into U s | t＝0 =F s / k s2 F can be obtained n =3kN, F s =1kN condition k s2 The value is 0.27 kN / mm.

[0095] In a certain tangential contact creep test, the parameter η s2 k s1 η s1 Determination of F n =3kN, F s Taking the experiment with a capacity of 1kN as an example, when determining the parameter k... s2After obtaining the value, use the function fitting function of Oringin software to input F. n =3kN, F s =1kN group of time-displacement test data, perform function fitting on formula (6) to obtain the fitted time-displacement curve, and then use F s =3kN, k s2 Substitute 0.27 kN / mm into the equation, and then solve for η using the coefficient term of time t. s2 k s1 η s1 The Oringin software automatically calculates the parameter η in this test based on the time-displacement curve data determined from the normal particle contact creep test. s2 =1762.75 kN·h / mm, k s1 =1.04kN / mm, η s1 = 7.79 kN·h / mm.

[0096] Repeat the above process to obtain the k values ​​corresponding to all load conditions of all other tangential contact creep tests in Table 3. s2 η s2 k s1 η s1 Values. Listed in Table 4.

[0097] Table 4 Calculation parameters for the tangential burgers model

[0098]

[0099] Observe the data and summarize k s2 The variation law under different load conditions is fitted to k. s2 The function expression, with F as the independent variable. n With normal load F n and tangential load F s As the independent variable, with k s1 Perform function fitting on the dependent variable to obtain k s1 With normal load F n Tangential load F s The function expression, with other parameters η s2 η s1 Similarly.

[0100] Tangential constitutive parameter k s2 η s2 k s1 η s1 With normal load F n Tangential load F s The expression for the relation is:

[0101] k s1=-0.365·F s +0.627·2.3 Fn / 3 (9)

[0102] η s1 =22.94·F s +1.7 (10)

[0103] k s2 =0.095·e 0.327·Fn (11)

[0104] η s2 =F s / 0.00083 (12)

[0105] At this point, all 10 parameters of the burgers model have been obtained, namely:

[0106] 1. The normal spring stiffness k of a Kelvin body n1 The corresponding software is bur_knk

[0107] 2. Normal spring stiffness k of a Maxwell body n2 The corresponding software is bur_cnk

[0108] 3. Normal viscosity coefficient η of Kelvin volume n1 The corresponding bur_knm in the software

[0109] 4. Normal viscosity coefficient η of Maxwell volume n2 The corresponding bur_knm in the software

[0110] 5. Tangential spring stiffness k of the Kelvin body s1 The corresponding software is bur_ksk

[0111] 6. Tangential spring stiffness k of a Maxwell body s2 The corresponding software is bur_csk

[0112] 7. The tangential viscosity coefficient η of Kelvin volume s1 The corresponding software is bur_ksm

[0113] 8. The tangential viscosity coefficient η of Maxwell volume s2 The corresponding software is bur_csm

[0114] The above eight parameters are represented by formulas (2)-(5) and (9)-(12) respectively, and are loaded into the discrete element software PFC.

[0115] 9. Coefficient of friction bur_fric

[0116] 10. Pull switch bur_notension.

[0117] Finally, the Burgers model in the Discrete Element Method (PFC) software was further developed using the Fish language, so that the eight parameters mentioned above in the model could become variables, that is, embedded in the PFC software in the form of function expressions. During the calculation process, the parameter values ​​are dynamically changed according to the load on the particles to achieve the purpose of accurately calculating particle contact creep deformation.

[0118] Using the time-displacement data points obtained from particle contact tests as the measured data from physical experiments, numerical calculations were performed on both normal and tangential particle contact tests according to the above scheme. The results of the numerical calculations were compared with the measured results from the physical experiments. The curve comparison effect was very good, such as... Figure 6 and Figure 7 As shown in the figure, the calculation accuracy is very high.

[0119] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A discrete element numerical simulation method for contact creep deformation of soil and rock particles, characterized in that, The method is used to simulate long-term contact creep between coarse particles, and includes the following steps: The Burgers models for normal coarse-grained contact creep and tangential coarse-grained contact creep are given by equations (1) and (6), respectively. Among them, U n F represents the normal displacement of the soil particles. n It is the normal load on the specimen, k n2 η n2 These are the normal spring stiffness and normal viscosity coefficient of a Maxwell body, k n1 η n1 These are the normal spring stiffness and normal viscosity coefficient of a Kelvin body; subscript n represents the normal direction; subscript s represents the tangential direction; t is time; U s F represents the tangential displacement of the soil particles. s It is the tangential load on the specimen, k s2 η s2 These are the tangential spring stiffness and tangential viscosity of a Maxwell body, k s1 η s1 These are the tangential spring stiffness and tangential viscosity of the Kelvin body; Determine the four parameters for each of the two burger models; The first step is to conduct normal particle contact creep tests to obtain the normal time-displacement curves of coarse particles under different normal loading conditions; a single normal particle contact creep test can determine a set of k... n2 η n2 k n1 η n1 These four values ​​are all related to the normal load F in this test. n Corresponding to the conditions; Under normal load F n Given the conditions, record the instantaneous displacement U corresponding to time t=0 during the normal particle contact creep test. n | t＝0 According to U n | t＝0 and F n Substitute the value into U n | t＝0 =F n / k n2 Obtain the parameter k under the current normal load. n2 The value; In determining parameter k n2 After obtaining the value, the time and normal displacement data under the normal load are obtained. Based on formula (1), function fitting is performed using Oringin software. After fitting, the normal load and the corresponding k are substituted into the data. n2 Then, based on the coefficient term of time t, η can be solved inversely. n2 k n1 η n1 ; Obtain the four parameters corresponding to all different normal loads, respectively, with the normal load F n With one variable as the independent variable and four parameters as the dependent variable, a function is fitted to obtain the normal constitutive parameters k. n2 η n2 k n1 η n1 With normal load F n The functional expression of the relation; The second step is to conduct a tangential particle contact creep test. In this test, a normal load is applied first, and then a tangential force is applied after stabilization. A single tangential particle contact creep test can determine a set of k values. s2 η s2 k s1 η ns1 These four values ​​are all related to the normal load F in this test. n and tangential load F s Corresponding to; Under tangential load F s Given the conditions, record the instantaneous displacement U corresponding to time t=0 during the tangential particle contact creep test. s | t＝0 According to U s | t＝0 and F s Substitute the value into U s | t＝0 =F s / k s2 Obtain the parameter k under the current tangential load. n2 The value; In determining parameter k s2 After obtaining the values, the data of time and tangential displacement under normal and tangential loads are obtained. Based on formula (6), function fitting is performed using Oringin software. After fitting, the tangential load and the corresponding k are substituted into the data. s2 Then, based on the coefficient term of time t, η can be solved inversely. s2 k s1 η s1 ; Obtain the four parameters corresponding to all different normal loads and different tangential loads, with the normal load F as the parameter. n As the independent variable, with k s2 Perform function fitting on the dependent variable to obtain k s2 With normal load F n The functional expression; with normal load F n and tangential load F s As the independent variable, with k s1 Perform function fitting on the dependent variable to obtain k s1 With normal load F n Tangential load F s The functional expression; with tangential load F s As the independent variable, with η s2 η s1 Perform function fitting on the dependent variable to obtain η. s2 η s1 Respectively with tangential load F s The function expression; The third step is to embed the functional expressions of the eight parameters and loads into the burgers model in PFC3D software, and change each parameter of the burgers model in PFC3D software to the above functional expressions. Once the input normal and tangential loads are determined, the parameters in the Burgers model can be dynamically adjusted, thereby obtaining the particle contact creep displacement under arbitrary load conditions and time.

2. The discrete element numerical simulation method for contact creep deformation of soil and rock particles according to claim 1, characterized in that, For the test specimens, normal particle contact creep test and tangential particle contact creep test were performed under different degrees of humidification. Obtain the normal constitutive parameter k under different humidification degrees. n2 η n2 k n1 η n1 With normal load F n The functional expression of the relation, and the tangential constitutive parameter k s2 With normal load F n The functional expression of the relation, k s1 With normal load F n Tangential load F s The function expression of η; s2 η s1 Respectively with tangential load F s The function expression; Based on the functional expression under natural moisture content conditions, the multiple relationship between different humidification degrees and natural conditions is determined, and this multiple relationship is denoted as the humidification coefficient. By adding a humidification coefficient input port to the PFC3D software, the parameters of the burgers model can be dynamically adjusted according to the input load and working conditions, thus obtaining particle contact creep displacement under arbitrary load conditions, working conditions and time.

3. The discrete element numerical simulation method for contact creep deformation of soil and rock particles according to claim 1, characterized in that, In PFC3D software, the burgers model includes ten parameters: Kelvin body normal spring stiffness k n1 The corresponding software is bur_knk The normal spring stiffness k of a Maxwell body n2 The corresponding software is bur_cnk The normal viscosity coefficient η of Kelvin's body n1 The corresponding bur_knm in the software The normal viscosity η of Maxwell volume n2 The corresponding bur_knm in the software Kelvin body tangential spring stiffness k s1 The corresponding software is bur_ksk tangential spring stiffness k of a Maxwell body s2 The corresponding software is bur_csk The tangential viscosity η of Kelvin's body s1 The corresponding software is bur_ksm Maxwell volume tangential viscosity η s2 The corresponding software is bur_csm The function expressions for the above eight parameters were recorded using the fish language and input into the burgers model of the PFC software to calculate the deformation of the particle contact test. The coefficient of friction, fric, takes extreme values. Set the tension switch bur_notension to 1.

4. The discrete element numerical simulation method for contact creep deformation of soil particles according to claim 1, characterized in that, The test subjects were cubic and conical soil particles with a diameter of 5 cm, which were subjected to point-to-surface contact.

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