Constructive model establishment method for predicting mechanical properties of rockfill material during cyclic loading and unloading

Abstract

The invention discloses a constitutive model building method for predicting mechanical characteristics of cyclic loading and unloading of rockfill materials, which comprises the following steps: on the basis of an elastic-plastic matrix of a generalized plastic model, introducing a function related to the number of cycles to describe the change of the elastic-plastic matrix along with the number of cycles; and the prediction capability of the loading and unloading modulus improvement model on the cyclic loading and unloading characteristics of the rockfill material under different confining pressure and stress levels is improved, and a new GPWHU constitutive model is formed. By adopting the technical scheme provided by the invention, the mechanical response of the rockfill material under cyclic loading and unloading can be accurately predicted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geotechnical engineering constitutive model design, and particularly relates to a constitutive model establishment method for predicting mechanical properties of rockfill under cyclic loading and unloading. BACKGROUND

[0002] Rockfill is the main filling material of earth-rock structures such as face rockfill dams, and its stress-strain properties under cyclic loading have an important influence on engineering safety. In the existing numerical simulation analysis method of rockfill dams, the commonly used constitutive models include the Duncan-Chang EB model, the Nanshui double-yield surface model and the generalized plasticity model. Among them, the Duncan EB model is the most widely used in the numerical simulation calculation of rockfill dams due to its simple parameters, clear physical meaning, and the ability to effectively capture the nonlinear deformation characteristics of rockfill. However, the model cannot reflect the dilatancy characteristics of rockfill, and due to the nature of its nonlinear elastic model, it cannot describe the deformation accumulation process of rockfill under cyclic loading and unloading. The Nanshui double-yield surface model is based on an elastoplasticity framework, and the model parameters are simple, and it overcomes the defects of nonlinear models that cannot consider dilatancy and stress-induced anisotropy, and has also been widely used. However, it still cannot accurately describe the deformation accumulation process of rockfill under cyclic loading and unloading. In contrast, the advantage of the generalized plasticity model is that it can better reflect the shear shrinkage, dilatancy and cyclic cumulative residual deformation of the material, and does not require strict definition of the yield function, hardening rule and flow rule, making it easy to improve the model. At present, many scholars have modified the generalized plasticity model to describe the mechanical properties of rockfill. However, the existing generalized plasticity model can only describe the mechanical properties of rockfill under single loading and unloading, and cannot describe the mechanical properties of rockfill under low-frequency multi-cycle cyclic loading and unloading due to water load, and further improvement is needed. Therefore, there is a certain demand in the industry to develop a constitutive model for predicting the mechanical properties of rockfill under cyclic loading and unloading SUMMARY To solve the problems in the prior art, the application provides a constitutive model establishment method for predicting the mechanical properties of rockfill under cyclic loading and unloading.

[0003] To achieve the above-mentioned purpose, the application provides the following solutions: A constitutive model establishment method for predicting the mechanical properties of rockfill under cyclic loading and unloading, comprising: S1: Collecting triaxial compression test stress and deformation data of rockfill of a face rockfill dam of a pumped storage power station under different stress paths.

[0004] S2: Adjusting the form of the generalized plasticity constitutive model according to the triaxial compression test stress and deformation data to form a GP_WHU constitutive model; wherein a function related to the number of cycles is added to the elastoplastic matrix of the GP_WHU model The item is improved, and the unloading and reloading modulus expressions are improved.

[0005] As a preference, the elastic-plastic matrix of the GP_WHU model is expressed as: The introduced function For reflecting the change of the plastic matrix with the increase of the cycle number n, it can be expressed as: Wherein, is the cycle number, is a dimensionless parameter; When the cycle reaches a predetermined number, there is , the new cycle will basically no longer produce plastic deformation.

[0006] As a preference, the plastic modulus form during loading and reloading is adjusted to: Wherein, is expressed as: Wherein, is the compression index, is a material parameter; and are respectively used to reflect the stress history and the hardening behavior of the material, and are expressed as: Wherein, and are dimensionless parameters, is the plastic volumetric strain.

[0007] The plastic modulus during unloading is adjusted to: Wherein, is the stress ratio during unloading, is a dimensionless parameter.

[0008] As a preference, according to the engineering characteristics, the mechanical parameters of the rockfill material of each rockfill area of the face rockfill dam of the pumped storage power station are calibrated: the mechanical parameters are the parameters of the GP_WHU model, and the parameters of the GP_WHU model include: the peak stress ratio coefficient and the peak stress ratio index , the shear dilation stress ratio coefficient and the shear dilation stress ratio index , the shear dilation equation coefficient and , the control compression characteristic parameter , , and d、 Loading and unloading coefficient , , and .

[0009] As preferred, based on the secondary development interface of the user-defined function of ANSYS finite element calculation software, the calculation subprogram of GP_WHU model is compiled, and is coupled with the calculation subprogram of five-parameter rheological model, the stress level and the minor principal stress are calculated, the rheological increment is calculated and is taken as initial strain for finite element incremental analysis, and the finite element analysis and prediction of the mechanical characteristics of the rockfill material under the rheological effect under cyclic loading and unloading are realized.

[0010] As preferred, the five parameters include: unloading times , stress ratio during unloading , historical maximum unloading stress ratio , plastic volume strain and cycle times ; wherein, and are used for determining the reloading process, when it is determined that loading and >0 and < , further determination is made for reloading; and are used for calculating the plastic modulus.

[0011] As preferred, an 8-node hexahedron element is used in ANSYS to simulate the loading process of the rockfill material in the laboratory test, and the prediction effect of the GP_WHU model under the complex stress path is verified.

[0012] Compared with the prior art, the beneficial effects of the present application are: The problem that the traditional model cannot describe the mechanical characteristics of the rockfill material under the low-frequency multiple cyclic loading and unloading effect of the water load is solved. The model can accurately simulate the phenomenon that the plastic deformation of the rockfill material gradually slows down until stable under the multiple cyclic load, by introducing the cycle function , and the influence of different confining pressures and stress levels on the material stiffness is more accurately reflected by using the modified unloading and reloading modulus, and the prediction accuracy of the stress-strain relationship under the complex path is improved. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the present application, the following briefly introduces the drawings needed to be used in the embodiments, obviously, the drawings described in the following are only some embodiments of the present application, and other drawings can also be obtained by the drawings for the ordinary skilled in the art without any creative labor.

[0014] Figure 1 The flow chart of the constitutive model establishment method for the rockfill material cyclic loading and unloading mechanical property prediction of the embodiments of the present application is shown in the figure. Figure 2 The unit body model schematic diagram of the present application is shown in the figure. Figure 3 The GP_WHU model subroutine calculation flow chart of the present application is shown in the figure. Figure 4 The GP_WHU model coupling five-parameter model subroutine calculation flow chart of the present application is shown in the figure. Figure 5 The unit body triaxial shear test prediction result figure of the present application is shown in the figure, wherein (a) is the main rockfill area and (b) is the secondary rockfill area. Figure 6 The unit body multiple cyclic loading and unloading test prediction result figure of the present application is shown in the figure. Figure 7 The finite element model figure of the certain face rockfill dam of the present application is shown in the figure. Figure 8 The water level amplitude area and the characteristic node distribution used for analysis of the certain face rockfill dam of the present application are shown in the figure. Figure 9 The GP_WHU model prediction result figure of the certain face rockfill dam of the present application is shown in the figure, which is the stress and deformation result figure of the typical profile of the dam body in the completion period and the impounding period. Figure 10 The GP_WHU model prediction result figure of the certain face rockfill dam of the present application is shown in the figure, which is the typical profile displacement distribution figure of the dam body in the frequent water level fluctuation period; wherein (a) is the settlement-water level after the first time to the dead water level, (b) is the settlement-200 times water level fluctuation to the normal impounding level, (c) is the river direction displacement-water level after the first time to the dead water level, (d) is the river direction displacement-200 times water level fluctuation to the normal impounding level, (e) is the total displacement-water level after the first time to the dead water level, and (f) is the total displacement-200 times water level fluctuation to the normal impounding level. Figure 11 The GP_WHU model prediction result figure of the certain face rockfill dam of the present application is shown in the figure, which is the typical profile stress distribution figure of the dam body in the frequent water level fluctuation period; wherein (a) is the stress state-water level after the first time to the dead water level, (b) is the stress state-200 times water level fluctuation to the normal impounding level, (c) is the large principal stress-water level after the first time to the dead water level, (d) is the large principal stress-200 times water level fluctuation to the normal impounding level, (e) is the small principal stress-water level after the first time to the dead water level, and (f) is the small principal stress-200 times water level fluctuation to the normal impounding level. Figure 12 This is the distribution of total displacement increment of a typical cross-section of a rockfill dam body caused by frequent water level fluctuations, as predicted by the GP_WHU model of a panel rockfill dam according to the present invention. Figure 13 The present invention describes the settlement evolution process of characteristic nodes of a panel rockfill dam predicted by the GP_WHU model. Figure 14 The diagram shows the panel displacement and stress distribution during frequent water level fluctuations predicted by the GP_WHU model of a rockfill dam panel according to the present invention; wherein, (a) deflection - water storage period (cm); (b) deflection - after 200 water level fluctuations (cm); (c) axial displacement - water storage period (cm); (d) axial displacement - after 200 water level fluctuations (cm); (e) slope stress - water storage period (cm); (f) slope stress - after 200 water level fluctuations (cm); (g) axial stress - water storage period (cm); (h) axial stress - after 200 water level fluctuations (cm). Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Example 1 like Figure 1 As shown, this invention provides a constitutive model establishment method for predicting the mechanical properties of riprap during cyclic loading and unloading, comprising: S1: Collect stress and deformation data of the rockfill material of the pumped storage power station panel rockfill dam under different stress paths in triaxial compression tests.

[0018] S2: Based on the stress-deformation data from triaxial compression tests, the generalized plastic constitutive model is adjusted to form the GP_WHU constitutive model; specifically, the elastoplastic matrix of the GP_WHU model is added... The item, and in the unloading and reloading modal expression, adopts replace .

[0019] S2.1: The elastoplastic matrix of the GP_WHU model is expressed as: S2.2: Introduced Functions For reflecting the change of plastic matrix with the increase of cycle number n, it can be expressed as: where, is the cycle number, is a dimensionless parameter. When the cycle reaches a certain number, there is , the new cycle will basically no longer produce plastic deformation.

[0020] S2.3: In order to better capture the difference of unloading and reloading behavior under different stress ratios, the form of plastic modulus during loading and reloading is adjusted as: where, is expressed as: where, is the compression index, is the material parameter; and are used to reflect the stress history and the hardening behavior of the material, respectively, and are expressed as: where, and are dimensionless parameters, is the plastic volumetric strain.

[0021] The plastic modulus during unloading is adjusted as: where, is the stress ratio during unloading, is a dimensionless parameter.

[0022] S3: According to the engineering characteristics, the mechanical parameters of the rockfill materials in each rockfill area of the pumped storage power station face panel rockfill dam are calibrated: GP_WHU model contains , , , , , , , , , d , , , and a total of 14 parameters (when a linear relationship is adopted, there are 10 parameters), and the calibration results are shown in Table 1.

[0023] S3.1: Peak stress ratio coefficient and peak stress ratio index Calibration: considering tensile strength of soil and rock , let , the failure strength of soil and rock is uniformly described as: where, is atmospheric pressure and tensile strength ; for rockfill and gravel, , , the average principal stress, .

[0024] The stress ratio of soil and rock at failure under different confining pressures ( ) is taken as the ordinate, and the corresponding time is taken as the abscissa to draw the relationship curve, and the peak stress ratio coefficient and the peak stress ratio index are fitted.

[0025] S3.2: Dilatancy stress ratio coefficient and dilatancy stress ratio index Calibration: is the stress ratio at the dilatancy and contractility phase point, which can be expressed by a linear relationship or a power function relationship, both of which can better reflect the dilatancy of soil and rock. If the dilatancy stress ratio is expressed by a linear relationship, the generalized shear stress at the time of dilatancy and contractility conversion of soil and rock under different confining pressures is taken as the ordinate, and the corresponding time average principal stress is taken as the abscissa to draw the relationship straight line, and the slope of the straight line is ; if the dilatancy stress ratio is expressed by a power function relationship, similarly, the generalized shear stress at the time of dilatancy and contractility conversion of soil and rock under different confining pressures is taken as the ordinate, and the corresponding time is taken as the abscissa to draw the relationship curve, and the dilatancy stress ratio coefficient and the dilatancy stress ratio index are fitted.

[0026] In actual calculation, in order to balance model simplification and calculation accuracy, the linear assumption is first used to describe the change trend of the dilatancy stress ratio, and then the power function relationship is used for correction in subsequent calculation, so as to more accurately reflect the dilatancy characteristics of soil and rock under different stress states.

[0027] S3.3: Dilatancy equation coefficient and Parameter calibration: The vertical axis is , Plotting the x-axis The dilatation equation curve can be fitted to obtain the dilatation equation coefficients. and , Let be the slope of the straight segment of the dilatation line. The condition that the curve begins to approach infinity under isotropic compression is defined. Distance between axes.

[0028] S3.4: Controlling compression characteristic parameters , , and d Calibration: When indoor isotropic compression test data is available, it can be determined through theoretical derivation; when indoor isotropic compression test data is unavailable, , , and d The determination can be made by referring to the inversion of the indoor triaxial test curve.

[0029] S3.5: Loading / Unloading Coefficient , , and Parameter calibration: Based on the results of the indoor single-cycle loading and unloading stress path test, an 8-node hexahedral element was used in ANSYS to simulate the single-cycle loading and unloading stress path test calibration of the rockfill material in the indoor test. The element schematic diagram is shown below. Figure 2 For a single loading and unloading path, a stress-controlled loading method is used, that is, axial stress that varies along a certain path is applied to the surface composed of nodes 5, 6, 7, and 8, causing the element to undergo shear deformation.

[0030] Table 1 S4: , as Figure 3 , 4 As shown, a calculation subroutine for the GP_WHU model is compiled based on the secondary development interface of User-Programmable Features (UPFs) provided by the ANSYS finite element analysis software. This subroutine introduces five state variables: the number of unloading operations. Stress ratio during unloading The historical maximum unloading stress ratio Plastic volumetric strain and number of loops .in, and The determination used in the reloading process is as follows: when it is determined to be loading, and the following conditions are met... >0 and Further determine to reload when the stress level is less than the stress level threshold value; and For the calculation of plastic modulus. The subroutine relies on the incremental finite element method for iterative solution, and adopts the Newton-Raphson (N-R) iterative algorithm with superior convergence and high calculation stability to efficiently solve nonlinear equations and ensure calculation accuracy and numerical stability.

[0031] S5: Coupling the GP_WHU model with the five-parameter rheological model, calculating the stress level and the minor principal stress The rheological increment is calculated and used as the initial strain for finite element incremental analysis.

[0032] S6: Using element test to verify the prediction effect of GP_WHU model under complex stress path. In ANSYS, an 8-node hexahedral element is used to simulate the loading process of rockfill material in laboratory test, and the element diagram is shown in Figure 2 .

[0033] S6.1: For triaxial shear stress path, displacement control loading method is adopted. The upper surface composed of nodes 5, 6, 7 and 8 is gradually subjected to axial displacement, causing shear deformation of the element, and the response parameters of the element are recorded during the loading process, including axial deformation (Z direction, compression is positive), volumetric deformation (volume shrinkage is positive) and deviatoric stress (defined as the difference between Z stress and confining pressure).

[0034] Figure 5 The triaxial test results of the dam material in each partition of a pumped storage power station under 0.3, 0.6, 0.9 and 1.2 MPa confining pressure and the prediction curves of EB model and GP_WHU model are shown. From the figure, it can be seen that due to the inability of EB model to consider shear dilation, the volumetric strain predicted by this model is significantly higher than the laboratory test value when the axial strain is large. In contrast, GP_WHU model can better predict the mechanical response of rockfill material under various confining pressures, showing higher prediction accuracy and applicability.

[0035] S6.2: For cyclic loading and unloading stress path, stress control and displacement control combined loading method is adopted. First, the deviatoric stress is applied to the upper surface composed of nodes 5, 6, 7 and 8, and then multiple cyclic loading and unloading are carried out; after the cycle is completed, the axial displacement is applied until the element is subjected to shear deformation. The change law of axial strain, volumetric strain and deviatoric stress of the element is recorded synchronously during the whole loading process to analyze the deformation characteristics under cyclic action.

[0036] Figure 6 ​The prediction results of GP model and GP_WHU model for dam material of a pumped storage power station under four stress levels and confining pressure are presented. By introducing the term, GP_WHU model can better reflect the convergence process of the deformation of rockfill material with the number of cycles; by adjusting the form of unloading and reloading modulus, the accuracy of the model in reflecting the axial cyclic cumulative deformation under different stress levels is improved; in addition, compared with GP model, the consistency of the volume deformation predicted by GP_WHU model after cyclic loading and unloading under different stress levels is stronger. In summary, GP_WHU model can better reflect the cyclic loading and unloading mechanical properties of rockfill material under different stress levels and confining pressures.

[0037] S7: Verify the accuracy and superiority of GP_WHU model according to the finite element calculation results of face rockfill dam. The finite element model of face rockfill dam (see Figure 7 ) is constructed to simulate the stress and deformation of the dam body during the three time periods of staged filling process, impoundment process and later water level fluctuation process. The impoundment process refers to the process of water level rising to the normal storage level, and the later water level fluctuation process refers to the cyclic fluctuation of water level between the normal storage level and the dead water level (see Figure 8 ), a total of 200 cyclic fluctuation processes are simulated.

[0038] As shown in Figure 9 , during the completion period, the stress state of most areas in the middle part of the dam is close to the stress state of triaxial test, while in the areas near the dam slope, the direction of the principal stress is approximately along the dam slope. After impoundment, the stress state of the middle part and the downstream side of the dam body remains basically unchanged, while the principal stress direction of the dam body near the upstream side of the dam slope deflects, and the direction of the major principal stress gradually deflects from the original direction along the dam slope to the direction perpendicular to the dam slope. After impoundment, the extreme values of the principal stresses of the dam body increase slightly. The impoundment process will cause significant settlement and riverwise displacement of the dam body near the upstream side of the dam slope, and the extreme values appear at about 1 / 3-1 / 2 of the dam height. After the action of cyclic water load, the deflection and axial displacement of the face plate further increase, and the extreme value of deflection moves to the top of the face plate, distributed at about 1 / 2 of the dam height.

[0039] Two representative moments are selected, when the water level first decreases to the dead water level and after 200 water level fluctuations, the water level returns to the normal storage level, and the displacement and stress distribution are drawn, as shown in Figure 10 and Figure 11 . When the water level first decreases to the dead water level, the displacement and stress value of the dam body are similar to those in the completion period of filling ( Figure 9 ). Due to the difference in water level, only in the area near the bottom of the upstream dam slope, the direction of total displacement and stress state are different. When the water level returns to the normal storage level after 200 water level fluctuations, the stress state and distribution of the dam body are similar to those in the impoundment period ( Figure 9The general consistency is as follows; however, in the area near the upstream dam slope ( Figure 10 (f) The shaded area is affected by frequent water level fluctuations, resulting in a significant increase in dam settlement and downstream displacement.

[0040] Figure 12 This paper illustrates the distribution of incremental deformation along a typical dam profile caused by frequent water level fluctuations between normal and dead water levels, specifically the difference between the dam deformation after 200 water level fluctuations and the deformation during the impoundment period. Under frequent water level fluctuations, significant cumulative deformation occurs near the upstream dam slope. As the height of the water level fluctuation zone increases, the impact of frequent water level fluctuations on dam deformation gradually expands, and the cumulative deformation increases accordingly, with the maximum cumulative deformation occurring near the lower limit of the water level fluctuation zone. Taking Scheme III, with a water level fluctuation zone height of 37m, as an example, the extreme value of the total displacement increment caused by frequent water level fluctuations accounts for approximately 78% of the extreme value of the total displacement increment caused by impoundment, indicating that its impact on dam displacement is significant when the water level fluctuation zone is large.

[0041] Select Figure 8 The feature nodes in the graph are used to plot their deformation and evolution process. For example... Figure 13 As shown, with the increase in the number of water level fluctuations, the settlement deformation at each point gradually increases and tends to converge. During the first 50 water level fluctuations, the settlement increment is relatively significant. After approximately 100 fluctuations, the settlement increment caused by subsequent water level fluctuations becomes very limited. Feature nodes B and C, located in the middle of the dam body and near the upstream slope, are more sensitive to frequent water level fluctuations, exhibiting more pronounced deformation rebound when the water level drops, and showing a larger settlement increment after 200 fluctuations. In contrast, feature node A, located at the top of the water level fluctuation zone, and feature nodes D, E, and F inside the dam body are less affected by frequent water level fluctuations, with relatively limited settlement changes.

[0042] Figure 14The displacement and stress distribution of the face slab after 200 water level fluctuations are further demonstrated. During the impoundment period, the maximum deflection of the face slab is distributed near the middle axis of the dam at about 1 / 3 of the dam height, while the maximum riverward displacement is distributed near the toe slab at about 1 / 2 of the dam height. The middle part of the face slab generates compressive stress in the downslope direction and the axial direction due to the impoundment process, while tensile stress is generated in the peripheral area of the face slab due to constraints, and there is a more obvious stress concentration phenomenon in some local areas. Compared with the impoundment period, after 200 water level fluctuations, the maximum deflection, the maximum upstream riverward displacement and the maximum downstream riverward displacement of the face slab increase by about 37%, 31% and 20%, respectively. At the same time, the position of the maximum deflection of the face slab moves up to the middle axis of the dam at about 1 / 2 of the dam height, which is mainly related to the fact that the influence area of the water level amplitude is closer to the top of the dam. In addition, under the action of frequent water level fluctuations, the stress values in the downslope direction and the axial direction of the face slab increase, and the stress concentration phenomenon in some areas on the left and right sides of the face slab is more obvious. This is mainly because the cumulative deformation of the cushion layer is further increased due to frequent water level fluctuations, which strengthens the tensile effect in the peripheral area of the face slab. The monitoring results show that the peripheral area of the face slab is a high-risk area of cracks, and when the tensile stress exceeds the tensile strength of the concrete face slab, it is easy to induce cracking. Therefore, for pumped storage face slab dams with frequent water level fluctuations, special attention should be paid to the problem of face slab cracking to ensure the safety of the structure.

[0043] The above-described embodiments are merely descriptions of the preferred modes of the present application and are not intended to limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design spirit of the present application shall fall within the scope of protection of the present application as defined by the claims.

Claims

1. A method for establishing a constitutive model for predicting mechanical properties of rockfill under cyclic loading and unloading, characterized in that, Comprising: S1: Collecting triaxial compression test stress and deformation data of face rockfill dam rockfill material of pumped storage power station under different stress paths. S2: According to the stress deformation data of triaxial compression test, the form of generalized plastic constitutive model is adjusted to constitute GP_WHU constitutive model; wherein a function related to the number of cycles is added in the elastic-plastic matrix of GP_WHU model Item, and improve the expression of unloading and reloading modulus.

2. The method for establishing the constitutive model for predicting the cyclic loading and unloading mechanical properties of rockfill material according to claim 1, characterized in that, The elastic-plastic matrix of GP_WHU model is expressed as: Introduced functions For reflecting the change of the plastic matrix as the number of cycles n increases, it can be expressed as: wherein is the number of cycles, is a dimensionless parameter; When the cycle is repeated a predetermined number of times, there is , the new cycle will essentially produce no plastic deformation.

3. The method according to claim 2, wherein, The form of plastic modulus at loading and reloading is adjusted as: wherein is represented by: where is the compression exponent, is the material parameter; and respectively reflect the stress history and the hardening behavior of the material, expressed as: wherein and is a dimensionless parameter, is the plastic volumetric strain. The plastic modulus at unloading is adjusted as: wherein is the stress ratio at unloading, is a dimensionless parameter.

4. The method for establishing a constitutive model for predicting cyclic loading and unloading mechanical properties of rockfill material according to claim 3, characterized in that, According to engineering characteristics, the mechanical parameters of the rockfill materials in each rockfill area of the face rockfill dam of the pumped storage power station are calibrated: the mechanical parameters are parameters of a GP_WHU model, and the parameters of the GP_WHU model include: a peak stress ratio coefficient and a peak stress ratio index , a shear dilation stress ratio coefficient and a shear dilation stress ratio index , a shear dilation equation coefficient and , a control compression characteristic parameter , , and d、 , a loading and unloading coefficient , , and .

5. The method for establishing a constitutive model for predicting cyclic loading and unloading mechanical properties of rockfill according to claim 4, characterized in that, Based on the secondary development interface of user-defined function of ANSYS finite element calculation software, the calculation subroutine of GP_WHU model is compiled and coupled with the calculation subroutine of five-parameter rheological model. Through the calculation of stress level and small principal stress The rheological increment is calculated and used as the initial strain for finite element incremental analysis, realizing the finite element analysis and prediction of the mechanical properties of rockfill materials under cyclic loading and unloading with rheological effect.

6. The method for establishing a constitutive model for predicting cyclic loading and unloading mechanical properties of rockfill material according to claim 5, characterized in that, Five parameters include: number of unloading , stress ratio at unloading , historical maximum unloading stress ratio , plastic volumetric strain , and number of cycles ; wherein, and are used for determining the reloading process, when the determination is loading, and the following conditions are satisfied > 0 and < , the further determination is reloading; and are used for calculating the plastic modulus.

7. The method according to claim 6, wherein, An 8-node hexahedral element is used in ANSYS to simulate the loading process of rockfill material in indoor test, and the prediction effect of GP_WHU model under complex stress path is verified.

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