Method for calculating creep damage strain of anisotropic rock

Abstract

The invention discloses an anisotropic rock creep damage strain calculation method, and belongs to the technical field of rock mechanics and engineering.The anisotropic rock creep damage strain calculation method comprises the steps that a strain softening model considering the aging characteristic is established, and on the basis of the strain softening model, the anisotropic characteristics of different bedding dip angles are considered, and a rock aging strain softening mechanism is also considered; finally, a one-dimensional creep damage constitutive model of the anisotropic rock comprehensively considering the different bedding dip angles is established and expanded to be three-dimensional, the creep damage strain of the anisotropic rock is obtained, and accurate prediction and description of the three-stage creep process of the stratified rock with the different bedding dip angles are achieved.

Description

Technical Field

[0001] The invention belongs to the field of rock mechanics and engineering technology, and in particular relates to a method for calculating anisotropic rock creep damage strain. Background Art

[0002] More and more rock engineering projects are gradually developing inside the slope rock mass. Due to the complexity of the original geological structure, considering the key geological factor of different bedding inclination angles is of great significance for studying the long-term stability of rock engineering. During the excavation process of slope rock engineering construction, physical and mechanical effects such as engineering excavation disturbance, unloading relaxation, and unloading rock structure evolution promote the derivation and penetration of rock cracks, the internal structure evolution gradually intensifies, and the bearing capacity of the layered rock mass is greatly reduced. With the accumulation of time, the deformation of the rock mass continues to develop, which will eventually lead to the instability and collapse of the rock mass. Therefore, it is becoming increasingly important to study the anisotropic creep mechanical properties of layered rocks and consider the influence of different bedding inclination angles on the creep deformation and destruction of rock masses.

[0003] Relevant scholars have conducted various studies on the anisotropy of rocks with different bedding angles, rock unloading creep, and creep constitutive models. For example, the literature "DENG Hua-feng, WANG Wei, LI Jian-lin, et al. Experimental study on anisotropic characteristics of bedded sandstone [J]. Chinese Journal of Rock Mechanics and Engineering, 2018, 37(1): 112-120." conducted triaxial compression tests on layered sandstone with significant bedding weak planes, and analyzed the effects and mechanisms of rock anisotropic mechanical properties, shear strength, and failure mode. For example, the literature "Xu Weiya, Yang Shengqi, Xie Shouyi. Study on triaxial rheological mechanical properties of greenschist [J]. Rock and Soil Mechanics, 2005, 26(4): 531–537." conducted triaxial compression creep tests with constant confining pressure and graded axial compression on the greenschist at the Jinping I hydropower station dam foundation, and studied the variation of the axial strain and lateral strain of the rock under different confining pressures with the specimen. For example, in the literature “ZHAO B, LIU D, DONG Q. Experimental research on creep behaviors of sandstone under uniaxial compressive and tensile stresses[J]. Journal of Rock Mechanics and Geotechnical Engineering, Volume 3, Supplement 1, 2011, Pages 438-444.”, a time-dependent nonlinear viscoplasticity was proposed, which was connected in series with the Burgers creep model to form a nonlinear viscoelastic-plastic creep constitutive model to describe the creep behavior of rock under uniaxial compressive and tensile stresses. Among them, the study of the creep constitutive model is one of the most important contents in creep research. It is necessary to adopt a suitable constitutive model according to the characteristics of the creep curve, and then inversely identify the parameters in the model to establish the constitutive equation between creep strain, stress and time to obtain the intrinsic connection between the three, thereby reflecting the creep deformation law and characteristics of rock.

[0004] The existing Chinese patent with application number 202311429609.6 discloses a method for constructing a nonlinear damage creep model for carbonaceous slate with different bedding angles. The scheme focuses on improving the existing Nishihara model, introducing elastic-plastic layered damage elements and nonlinear viscous damage elements, and emphasizing the nonlinear damage characteristics of the model. The specific elements of this scheme are composed of an ideal viscoplastic body (a pair of friction plates and a damper in parallel), a Kelvin body (a Hookean body and a Newtonian body in parallel), an elastic-plastic layered damage element, and a nonlinear viscous damage element. It aims to overcome the problem that the existing model cannot describe accelerated creep, and its application field mainly focuses on tunnel engineering.

[0005] In summary, it can be seen that the above research results have laid a good foundation for the analysis of anisotropic mechanical properties of rocks, unloading creep mechanics and constitutive model analysis. However, related studies mainly focus on single factor analysis, and rarely analyze the anisotropic unloading creep deformation characteristics and constitutive models of rocks with different bedding angles. The traditional single elastic-viscoplastic model does not consider the influence of bedding angle and strain softening in the creep deformation process. Therefore, it is impossible to accurately predict and describe the three-stage process of creep of layered rocks with different bedding angles. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for calculating anisotropic rock creep damage strain, which solves the problem that the prior art cannot accurately predict and describe the three-stage creep process of layered rocks with different bedding angles.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is: A method for calculating anisotropic rock creep damage strain is provided, which comprises the following steps: S1. Establish a strain softening model considering the time-dependent characteristics for the accelerated creep process of rock; S2. Introduce a plastic body B&D element containing a bedding inclination factor into the strain softening model considering the aging characteristics, establish a one-dimensional creep damage constitutive model considering the anisotropic characteristics of different bedding inclinations and the dual mechanism of aging-induced strain softening, and obtain the corresponding constitutive equation of the one-dimensional creep damage constitutive model; S3. According to the elastic-plastic mechanics theory, the constitutive equation corresponding to the one-dimensional creep damage constitutive model is extended to three dimensions, and the constitutive equation corresponding to the three-dimensional creep damage constitutive model is obtained; S4. The constitutive equation corresponding to the three-dimensional creep damage constitutive model is combined with the spherical strain tensor to obtain the three-dimensional axial creep equation, that is, the anisotropic rock creep damage strain.

[0008] Furthermore, the method for establishing the strain softening model considering the aging characteristics is as follows: A Burgers model element and a Stain-Softening element are connected in series to obtain a strain softening model considering the aging characteristics. The expression of the strain softening model considering the aging characteristics is:

[0009] in is the total strain of the strain softening model considering the aging characteristics; for stress; is the elastic modulus of the Maxwell body; is the viscosity coefficient of the Maxwell body; is the viscoelastic modulus of the Kelvin body; is the viscosity coefficient of the Kelvin body; t is the total time; It represents the exponent with the natural constant e as the base; is the plastic strain of the strain softening model considering the aging characteristics.

[0010] Further, the area of ​​the plastic body B&D element containing the bedding inclination factor in step S2 is The damaged area is The undamaged area is , the damaged part and the undamaged part are in parallel state; during the stress loading process, when the damaged part does not work, the plastic B&D element containing the bedding inclination factor is an elastic element, and the undamaged part satisfies the Hookean law; the creep constitutive equation of the plastic B&D element containing the bedding inclination factor is expressed as:

[0011] in and Both represent the plastic strain of the B&D element of the plastic body with the bedding inclination factor; represents the elastic modulus of the plastic B&D element including the bedding inclination factor; is the creep failure moment of the plastic B&D element with bedding inclination factor; is the bedding dip Related damage functions; It represents the creep damage initiation time of the plastic B&D element including the bedding inclination factor.

[0012] Furthermore, the one-dimensional creep damage constitutive model in step S2 is composed of a Maxwell body, a Kelvin body, a strain softening model considering aging characteristics, and a plastic body B&D element containing a bedding inclination factor connected in series in sequence; the expression of the constitutive equation corresponding to the one-dimensional creep damage constitutive model is:

[0013] in is the strain of the constitutive equation corresponding to the one-dimensional creep damage constitutive model; It represents the critical stress threshold at which steady-state creep occurs in the one-dimensional creep damage constitutive model.

[0014] Furthermore, the constitutive equation corresponding to the three-dimensional creep damage constitutive model in step S3 is expressed as:

[0015] in is the strain of the three-dimensional creep damage constitutive model, that is, the anisotropic rock creep damage strain; is the shear modulus of the Hooke body; is the stress deflection tensor of the three-dimensional creep damage constitutive model; K is the bulk modulus of the three-dimensional creep damage constitutive model; is the spherical stress tensor of the three-dimensional creep damage constitutive model; is the Krobecker function; is the viscoelastic shear modulus of the Kelvin body; F is the yield function of the rock; is the viscosity coefficient of the plastic B&D element; represents the power function; is the yield reference value; is the plastic potential function of rock; is the total stress tensor of the three-dimensional creep damage constitutive model.

[0016] Furthermore, the spherical strain tensor in step S4 is , the expression of the three-dimensional axial creep equation is:

[0017] in and They are the first principal stress and the second principal stress in the multi-stage loading-graded unloading triaxial creep test.

[0018] The beneficial effects of the present invention are: 1. The present invention establishes a strain softening model that takes time-dependent characteristics into consideration. On the basis of the strain softening model, it not only takes into account the anisotropic characteristics of different bedding angles, but also takes into account the time-dependent strain softening mechanism of rocks. Finally, a one-dimensional creep damage constitutive model of anisotropic rocks with different bedding angles is established, and the model is extended to three dimensions to obtain the anisotropic rock creep damage strain, thereby realizing the accurate prediction and description of the three-stage creep process of layered rocks with different bedding angles.

[0019] 2. The present invention focuses on the dual mechanism of anisotropic characteristics of the model and time-dependent softening, rather than the single factor of layered damage elements in the prior art. The present invention can be used to study the creep mechanical properties of layered rock slope engineering under excavation unloading conditions, and provide a certain reference for the engineering stability design of layered rock masses with different bedding angles.

[0020] 3. The one-dimensional creep damage constitutive model (improved LSVISC model) proposed in the present invention has a higher degree of fit for the creep curve of anisotropic layered rocks under the influence of different bedding angles, and can more accurately describe the deformation characteristics of the three stages of layered rock creep, solving the shortcoming that the traditional Burgers model cannot describe the accelerated creep stage. The improved LSVISC model has wide applicability for describing the creep deformation characteristics of layered rocks with different bedding angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the process of this method; Figure 2 is the strength degradation curve of the Stain-Softening strain softening model introduced in the present invention; Figure 3 It is the plastic body B&D element containing the bedding inclination factor introduced in the present invention; Figure 4 A one-dimensional creep damage constitutive model (improved LSVISC model) is proposed to consider the dual mechanisms of anisotropic characteristics of different bedding angles and time-dependent strain softening. Figure 5 The full process curve of triaxial creep under multi-stage loading and graded unloading of rock with 0° bedding inclination according to the embodiment of the present invention; Figure 6 The full process curve of triaxial creep under multi-stage loading and graded unloading of rock with a bedding angle of 30° according to an embodiment of the present invention; Figure 7 A cluster of axial creep curves of multi-stage loading and graded unloading at a 45° bedding inclination angle according to an embodiment of the present invention; Figure 8 It is a cluster of 45° bedding inclination multi-stage loading-stage unloading circumferential creep curves of an embodiment of the present invention; Fig. 9 60° bedding inclination angle axial steady-state creep rate and deviator stress relationship curve of the embodiment of the present invention; Fig.10 It is a comparison diagram of the 30° bedding dip test point of the embodiment of the present invention, the traditional Burgers model, and the improved LSVISC model; Fig.11 It is a comparison diagram of the 90° bedding dip test point of the embodiment of the present invention, the traditional Burgers model and the improved LSVISC model. DETAILED DESCRIPTION

[0022] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0023] like Figure 1 , Figure 2 and Figure 3 As shown, the calculation method of the anisotropic rock creep damage strain includes the following steps: S1. Establish a strain softening model considering the time-dependent characteristics for the accelerated creep process of rock; S2. Introduce a plastic body B&D element containing a bedding inclination factor into the strain softening model considering the aging characteristics, establish a one-dimensional creep damage constitutive model considering the anisotropic characteristics of different bedding inclinations and the dual mechanism of aging-induced strain softening, and obtain the corresponding constitutive equation of the one-dimensional creep damage constitutive model; S3. According to the elastic-plastic mechanics theory, the constitutive equation corresponding to the one-dimensional creep damage constitutive model is extended to three dimensions, and the constitutive equation corresponding to the three-dimensional creep damage constitutive model is obtained; S4. The constitutive equation corresponding to the three-dimensional creep damage constitutive model is combined with the spherical strain tensor to obtain the three-dimensional axial creep equation, that is, the anisotropic rock creep damage strain.

[0024] The method for establishing the strain softening model considering the aging characteristics is: A Burgers model element and a Stain-Softening element are connected in series to obtain a strain softening model considering the aging characteristics. The expression of the strain softening model considering the aging characteristics is:

[0025] in is the total strain of the strain softening model considering the aging characteristics; for stress; is the elastic modulus of the Maxwell body; is the viscosity coefficient of the Maxwell body; is the viscoelastic modulus of the Kelvin body; is the viscosity coefficient of the Kelvin body; t is the total time; It represents the exponent with the natural constant e as the base; is the plastic strain of the strain softening model considering the aging characteristics.

[0026] In stress Under the action of the strain softening model considering the aging characteristics, the total strain and The corresponding Equal, the balanced equation is expressed as:

[0027] During stress loading, the damaged area in the layered damaged element When no action is taken, the plastic B&D element containing the bedding inclination factor degenerates into an elastic element, and the undamaged area The Hookean law is satisfied as follows:

[0028] in are the stress, elastic modulus and strain of the undamaged part respectively.

[0029] It can be obtained that the damage variable of the damaged part of the plastic B&D element containing the bedding dip factor (that is, the nonlinear bedding dip damage B&D element) is:

[0030] According to the stress-strain relationship criterion of the parallel relationship of the B&D elements of the plastic body with the bedding inclination factor, , we can get:

[0031] Considering nonlinear bedding dip damage variables , the bedding dip Substituting the function expression into the above formula, the creep constitutive equation of the plastic B&D element containing the bedding inclination factor can be obtained.

[0032] The area of ​​the plastic body B&D element containing the bedding inclination factor in step S2 is The damaged area is The undamaged area is , the damaged part and the undamaged part are in parallel state; during the stress loading process, when the damaged part does not work, the plastic B&D element containing the bedding inclination factor is an elastic element, and the undamaged part satisfies the Hookean law; the creep constitutive equation of the plastic B&D element containing the bedding inclination factor is expressed as:

[0033] in and Both represent the plastic strain of the B&D element of the plastic body with the bedding inclination factor; represents the elastic modulus of the plastic B&D element including the bedding inclination factor; is the creep failure moment of the plastic B&D element with bedding inclination factor; is the bedding dip Related damage functions; It represents the creep damage initiation time of the plastic B&D element including the bedding inclination factor.

[0034] In step S2, the one-dimensional creep damage constitutive model is composed of Maxwell body, Kelvin body, strain softening model considering aging characteristics and plastic body B&D elements containing bedding inclination factor connected in series. It should be noted that the positional relationship between these model elements has no effect, and the sequential connection is only a feasible implementation method. According to the basic characteristics of each element and the stress action, according to the Boltzmann superposition principle, the expression of the constitutive equation corresponding to the one-dimensional creep damage constitutive model is:

[0035] in is the strain of the constitutive equation corresponding to the one-dimensional creep damage constitutive model; It represents the critical stress threshold for steady-state creep of the one-dimensional creep damage constitutive model, that is, the stress threshold of the Stain-Softening element. When , the one-dimensional creep damage constitutive model obeys the non-associated shear and associated tensile flow rules, and the constitutive relation of deformation flow is obtained.

[0036] In the Stain-Softening strain softening element, the relationship between plastic strain and rock and soil parameters is expressed by a linear function or a linear piecewise function:

[0037] in For cohesion; is the internal friction angle; is the tensile strength; is the ultimate shear plastic strain; is the ultimate tensile plastic strain; when the degradation function curve is a horizontal line, it degenerates into a general ideal plastic model.

[0038] In a three-dimensional stress state, the stress tensor Can be decomposed into a spherical stress tensor and the stress deflection tensor , and its equilibrium relationship is expressed as:

[0039] For the Hooke body, according to the generalized Hooke law, the three-dimensional constitutive relationship of the elastic body is:

[0040] in, is the Hooke body strain, is the Krobecker function, and K are the shear modulus and bulk modulus, respectively.

[0041] Similarly, assuming that the volume change of rock is elastic, the three-dimensional constitutive equation of Kelvin body is:

[0042] in, is the Kelvin body strain, is the viscoelastic shear modulus.

[0043] For viscoplastic bodies, according to the generalized law of plasticity, its three-dimensional constitutive relation is:

[0044] in, is the viscoplastic volume strain; is the rock yield function; is the yield reference value; g is the plastic potential function of rock.

[0045] The Mohr-Coulomb yield criterion is used to describe the plastic deformation law of rock, and there are shear and tension yield in the main space:

[0046]

[0047] in, and Define the maximum principal stress and the minimum principal stress respectively; c is the cohesion of rock; φ is the internal friction angle.

[0048] Potential Function g It is expressed as:

[0049]

[0050] In the formula is the dilatancy angle; is the potential function of shear plastic flow; is the potential function of tensile plastic flow.

[0051] definition is the time-dependent damage strain threshold, when When , the rock enters the damage stage and its creep parameters begin to change. Therefore, the constitutive equation corresponding to the three-dimensional creep damage constitutive model in step S3 is expressed as:

[0052] in is the strain of the three-dimensional creep damage constitutive model, that is, the anisotropic rock creep damage strain; is the shear modulus of the Hooke body; is the stress deflection tensor of the three-dimensional creep damage constitutive model; K is the bulk modulus of the three-dimensional creep damage constitutive model; is the spherical stress tensor of the three-dimensional creep damage constitutive model; is the Krobecker function; is the viscoelastic shear modulus of the Kelvin body; F is the yield function of the rock; is the viscosity coefficient of the plastic B&D element; represents the power function; is the yield reference value; is the plastic potential function of rock; is the total stress tensor of the three-dimensional creep damage constitutive model.

[0053] The spherical strain tensor in step S4 is , the expression of the three-dimensional axial creep equation is:

[0054] in and They are the first principal stress and the second principal stress in the multi-stage loading-graded unloading triaxial creep test.

[0055] In the specific implementation process, based on the results of multi-stage loading-graded unloading triaxial creep test, the Levenberg-Marquardt (LM) algorithm + general global optimization method can be used to solve and identify the parameters of the one-dimensional creep damage constitutive model considering the anisotropic characteristics of different bedding angles and the dual mechanism of time-induced strain softening. The model parameters obtained by solving and identifying are substituted into the three-dimensional creep damage constitutive model to obtain the calculation results of the three-dimensional creep damage constitutive model. The calculation results of the three-dimensional creep damage constitutive model are compared with the creep test data and the traditional Burgers model to verify the reliability of this method.

[0056] In one embodiment of the present invention, the multi-stage loading-stage unloading triaxial creep test of layered rocks with different bedding angles is controlled by a ROCK600-50VHT rock multi-field multi-phase triaxial rheological loading system, and an axial pressure-unloading confining pressure test scheme is adopted. The initial confining pressure σ3 is 20MPa, and the unloading is carried out at a rate of 0.05MPa / s, and the unloading confining pressure stress gradient is 5% σ 3. 10% σ 3. 15% σ 3. 20% σ 3. 25% σ 3. Multi-stage loading axial compression to obtain 40% of the rock peak stress intensity σ p 50% σ p 60% σ p 70% σ p 80% σ p , multi-stage loading was performed at a rate of 0.05MPa / s, and the cycle operation was continued until the specimen failed. The test scheme of triaxial creep stress level for rocks with different bedding inclination angles is shown in Table 1.

[0057] Table 1: Test scheme for triaxial creep stress level of rocks with different bedding inclination angles under multi-stage loading

[0058] In Table 1, Z1~Z5 are the axial compression deviator stress levels. σ p is the peak deviator stress level of the conventional triaxial compression test, MPa.

[0059] The multi-stage loading-stage unloading triaxial creep data of layered rocks with different bedding angles are obtained, and the creep relationship curves of the whole process of rocks with bedding angles of 0° and 30° are drawn based on the creep data, such as Figure 5 , Figure 6 shown.

[0060] According to the linear superposition principle, the multi-stage loading-stage unloading triaxial creep test data were processed to draw the creep axis and radial strain-time relationship curves of different stress levels under 45° bedding inclination, as shown in Figure 2. Figure 7 , Figure 8 shown.

[0061] Based on the data of triaxial creep tests under multi-stage loading and graded unloading, the steady-state creep rate method is used to draw the relationship curve between the steady-state creep rate and the deviatoric stress of the rock with a bedding inclination angle of 60°, and the inflection point on the steady-state creep rate-stress level relationship curve is used as an important indicator reflecting the long-term strength of the rock, such as Fig. 9 shown.

[0062] On the basis of the Burgers model, the Stain-Softening strain softening element is connected in series to establish a strain softening mechanical model considering the time-dependent characteristics. Then, the plastic body B&D element containing the bedding inclination factor is introduced for characterization. A one-dimensional creep damage constitutive model considering the anisotropic characteristics of different bedding inclinations and the dual mechanism of time-dependent strain softening is constructed, such as Figure 4 shown.

[0063] Based on the creep equation of the element, the three-dimensional axial creep equation (i.e., the creep damage constitutive equation of anisotropic rocks considering different bedding inclination angles) is established as shown below.

[0064]

[0065] According to the creep strain-time relationship curve, the one-dimensional creep damage constitutive model considering the anisotropic characteristics of different bedding angles and the dual mechanism of time-dependent strain softening was identified to obtain the creep model parameters. The Levenberg-Marquardt (LM) algorithm + general global optimization method in 1StOpt was used to solve the model parameters, and the identified LSVISC model parameters were solved, as shown in Table 2.

[0066] Table 2: Results of improved LSVISC creep model parameters for 30° bedding angle loading and unloading test

[0067] Substitute the identified model parameters into the three-dimensional creep damage constitutive model, and compare the calculation results of the three-dimensional creep damage constitutive model with the experimental data, such as Fig.10 , Fig.11 As shown in the figure, this method can accurately describe the whole process characteristics of attenuation creep, steady-state creep and accelerated creep of layered rocks with different bedding angles, accurately reflect the creep damage characteristics of layered rocks with different bedding angles under excavation unloading conditions, and provide an important theoretical basis for the long-term stability design of layered rock and soil engineering with different bedding angles.

[0068] In summary, this method first constructs a strain softening model, and then introduces a plastic body B&D element containing a bedding inclination factor into the strain softening model. The specific elements are composed of Maxwell bodies (a spring and a damper), Kelvin bodies, a strain softening model considering time-dependent characteristics, and plastic body B&D elements containing bedding inclination factors. A one-dimensional creep damage constitutive model is constructed and extended to three dimensions to calculate the corresponding strain. This method is suitable for studying various types of layered rock mass engineering, especially for simulating the creep mechanical properties of layered rock mass slopes under real excavation and unloading conditions. It not only analyzes the anisotropic characteristics of rocks, but also considers the long-term creep strength and strain softening efficiency of rocks. The application fields and factors considered are more extensive and comprehensive than the former, and can provide a theoretical basis for the design and construction of various types of layered rock mass stability engineering.

Claims

1. A method for calculating anisotropic rock creep damage strain, characterized in that: The following steps are involved: S1. Establish a strain softening model considering the time-dependent characteristics for the accelerated creep process of rock; S2. Introduce a plastic body B&D element containing a bedding inclination factor into the strain softening model considering the aging characteristics, establish a one-dimensional creep damage constitutive model considering the anisotropic characteristics of different bedding inclinations and the dual mechanism of aging-induced strain softening, and obtain the corresponding constitutive equation of the one-dimensional creep damage constitutive model; S3. According to the elastic-plastic mechanics theory, the constitutive equation corresponding to the one-dimensional creep damage constitutive model is extended to three dimensions, and the constitutive equation corresponding to the three-dimensional creep damage constitutive model is obtained; S4. The constitutive equation corresponding to the three-dimensional creep damage constitutive model is combined with the spherical strain tensor to obtain the three-dimensional axial creep equation, that is, the anisotropic rock creep damage strain.

2. The method for calculating anisotropic rock creep damage strain according to claim 1, characterized in that: The method for establishing the strain softening model considering the aging characteristics is: A Burgers model element and a Stain-Softening element are connected in series to obtain a strain softening model considering the aging characteristics. The expression of the strain softening model considering the aging characteristics is: in is the total strain of the strain softening model considering the aging characteristics; for stress; is the elastic modulus of the Maxwell body; is the viscosity coefficient of the Maxwell body; is the viscoelastic modulus of the Kelvin body; is the viscosity coefficient of the Kelvin body; t is the total time; It represents the exponent with the natural constant e as the base; is the plastic strain of the strain softening model considering the aging characteristics.

3. The method for calculating anisotropic rock creep damage strain according to claim 2, characterized in that: The area of ​​the plastic body B&D element containing the bedding inclination factor in step S2 is The damaged area is The undamaged area is , the damaged part and the undamaged part are in parallel state; during the stress loading process, when the damaged part does not work, the plastic B&D element containing the bedding inclination factor is an elastic element, and the undamaged part satisfies the Hookean law; the creep constitutive equation of the plastic B&D element containing the bedding inclination factor is expressed as: in and Both represent the plastic strain of the B&D element of the plastic body with the bedding inclination factor; represents the elastic modulus of the plastic B&D element including the bedding inclination factor; is the creep failure moment of the plastic B&D element with bedding inclination factor; is the bedding dip Related damage functions; It represents the creep damage initiation time of the plastic B&D element including the bedding inclination factor.

4. The method for calculating anisotropic rock creep damage strain according to claim 3, characterized in that: The one-dimensional creep damage constitutive model in step S2 is composed of Maxwell body, Kelvin body, strain softening model considering aging characteristics and plastic body B&D elements containing bedding inclination factor connected in series in sequence; the constitutive equation corresponding to the one-dimensional creep damage constitutive model is expressed as: in is the strain of the constitutive equation corresponding to the one-dimensional creep damage constitutive model; It represents the critical stress threshold at which steady-state creep occurs in the one-dimensional creep damage constitutive model.

5. The method for calculating anisotropic rock creep damage strain according to claim 4, characterized in that: The constitutive equation corresponding to the three-dimensional creep damage constitutive model in step S3 is expressed as: in is the strain of the three-dimensional creep damage constitutive model, that is, the anisotropic rock creep damage strain; is the shear modulus of the Hooke body; is the stress deflection tensor of the three-dimensional creep damage constitutive model; K is the bulk modulus of the three-dimensional creep damage constitutive model; is the spherical stress tensor of the three-dimensional creep damage constitutive model; is the Krobecker function; is the viscoelastic shear modulus of the Kelvin body; F is the yield function of the rock; is the viscosity coefficient of the plastic B&D element; represents the power function; is the yield reference value; is the plastic potential function of rock; is the total stress tensor of the three-dimensional creep damage constitutive model.

6. The method for calculating anisotropic rock creep damage strain according to claim 5, characterized in that: The spherical strain tensor in step S4 is , the expression of the three-dimensional axial creep equation is: in and They are the first principal stress and the second principal stress in the multi-stage loading-graded unloading triaxial creep test.

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