Method for deducing jointed rock-soil body material creep model based on complete rock-soil material creep model

Abstract

The invention discloses a method for deducing a jointed rock-soil body material creep model based on a complete rock-soil material creep model, which comprises the following steps: carrying out a uniaxial compression creep test on a complete rock sample and a crack sample, establishing a relationship between a complete rock and a crack rock body, constructing an aging damage function D (t), obtaining an improved classical Burgers model constitutive equation, and calculating a joint rock-soil body material creep model according to the improved classical Burgers model constitutive equation. Calculating an expression of an initial damage variable D0 to obtain a simplified complete sample fitting parameter; deriving a creep model of the fractured rock mass from the creep model of the complete rock; and verifying the model. According to the method, by establishing the relation between the complete rock-soil material and the fractured rock-soil material, the creep model of the rock-soil material containing different fractures is deduced from the complete rock-soil material creep model and is used for describing the creep process of the rock-soil material containing different fractures, and the actual applicability and universality of the creep model are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rock engineering, and in particular relates to a method for deriving a creep model of a jointed rock-soil material based on a creep model of a complete rock-soil material. Background Art

[0002] A suitable creep model is crucial for analyzing the time-dependent characteristics of engineering rock mass. At present, there are two main methods for establishing the creep model of fractured rock mass: one is from the perspective of fracture mechanics, when the stress intensity factor is between the critical stress intensity of subcritical crack extension and the fracture toughness, the subcritical crack extends at a certain speed; the other is based on damage mechanics, by introducing the rock mass creep damage to describe the damage process. Existing research results have increased our understanding of the creep characteristics of fractured rock mass, but existing research cannot give a good description of the influence of cracks on the creep process of rock mass, especially the accelerated creep stage; at the same time, due to the complexity and diversity of crack distribution in practice, indoor tests cannot cover all situations of actual cracks. If the connection between the creep model of intact rock and rock mass with cracks can be established, the creep model of rock mass with different cracks can be derived from the creep model of intact rock obtained from indoor tests, thereby greatly improving its possibility of application in actual engineering. Therefore, it is necessary to design a method to derive the creep model of jointed rock mass material based on the creep model of intact rock material to solve the above problems. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for deriving a creep model of a jointed rock and soil material based on a creep model of a complete rock and soil material. The method establishes a connection between the complete rock and the fractured rock mass, and derives a creep model of the rock mass containing different fractures from the complete rock creep model to describe the creep process of the rock mass containing different fractures, thereby improving the practical applicability and universality of the creep model.

[0004] In order to achieve the above technical effects, the technical solution adopted by the present invention is:

[0005] A method for deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material comprises the following steps:

[0006] S1, uniaxial compression creep tests are carried out on intact rock specimens and fractured rock specimens under different stresses to obtain creep curves of each specimen;

[0007] S2, the correlation between fractured rock mass and intact rock is established using Lemaitre strain equivalence principle, and Kachanov law is used to describe the time-dependent damage function D(t) of rock specimens in the accelerated creep stage;

[0008] S3, the attenuation and steady-state creep process of the specimen is described by the classic Burgers model constitutive equation, and the aging damage body E3,D(t) is introduced into the classic Burgers model constitutive equation to obtain the improved Burgers model constitutive equation reflecting the mechanical behavior of the entire creep process;

[0009] S4, the expression of the initial damage variable D0 is obtained based on the relationship between the unit volume strain energy of intact rock and fractured rock mass;

[0010] S5, selecting a suitable creep model for fitting according to the stress state of the sample, obtaining fitting parameters of the complete rock sample under different stresses, and simplifying the fitting parameters of the complete sample under different stresses;

[0011] S6, according to step 4, the initial damage variable D0 of different fractured specimens is calculated, and then combined with the simplified fitting parameters in step 5, it is substituted into the constitutive equation of the improved Burgers model to obtain the creep model of the fractured rock mass derived from the creep model of the intact rock.

[0012] Preferably, in step S1, the fractured specimen has prefabricated fractures with different geometric shapes compared to the intact specimen.

[0013] Preferably, in step S2, the Lemaitre strain equivalence principle equates the strain caused by the apparent stress applied to the damaged material to the strain caused by the equivalent stress acting on the undamaged material:

[0014]

[0015] Based on this, the relationship between intact rock and fractured rock mass can be expressed as:

[0016]

[0017] Where D is the damage variable.

[0018] Preferably, in step S2, the relationship between D(t) and σ1 is described as follows according to Kachanov's law:

[0019]

[0020] In the formula, C and n are rock material constants; σ1 is the stress on the rock;

[0021] Based on the above formula, according to the two boundary conditions D(t=0)=0 (when t=0, the material is not damaged), D(t=t F )=1(when t=t F , the material is completely damaged) and the rock damage evolution equation under creep state is derived as follows:

[0022]

[0023] In the formula, t F is the time of creep damage; take r=1 / (n+1).

[0024] Preferably, in step S3, the constitutive equation of the classic Burgers model is:

[0025]

[0026] Where, E1 is the instantaneous elastic modulus; E2 is the viscoelastic modulus; η1, η2 are the viscosity coefficients; σ L Long-term strength of rock mass.

[0027] Preferably, in step S3, the aging damaged body E3,D(t) is introduced into the constitutive equation of the classic Burgers model, and the constitutive equation of the improved Burgers model is obtained as follows:

[0028]

[0029] Where, E1 is the instantaneous elastic modulus; E2 is the viscoelastic modulus; η1, η2 are the viscosity coefficients; σ L Long-term strength of rock mass.

[0030] Preferably, in step S4, under uniaxial compression conditions, the elastic strain energy per unit volume of intact rock and rock mass containing fractures has the following relationship:

[0031]

[0032] In the formula, ΔU E is the unit elastic strain energy increased due to the existence of cracks, ΔU E The expression is:

[0033]

[0034] Combined ΔU E The final expression of the initial damage variable can be obtained by using the expression of

[0035]

[0036] Where U E and U E0 are the unit elastic strain energies of fractured rock and intact rock, respectively, and E0 is the elastic modulus of intact rock.

[0037] Preferably, in step S5, when the stress σ1≤σ L When the stress of the specimen is σ1>σ LWhen , the improved Burgers model is selected for fitting. The fitting values ​​of model parameters E1, E2, E3, r, η1, and η2 are obtained through fitting.

[0038] Preferably, in step S5, the method for simplifying the fitting parameters of the complete specimen under different stresses is: by controlling other parameters unchanged, changing the parameters to be simplified, and observing the changes in the creep curve; and selecting appropriate parameter values ​​according to the influence of the parameters on the creep process.

[0039] Preferably, in step S6, the creep model of the intact rock is used to derive the creep model of the fractured rock mass by substituting the initial damage variable D0 of the fractured rock sample and the simplified creep parameters of the intact rock into the constitutive equation of the improved Burgers model.

[0040] The beneficial effects of the present invention are as follows:

[0041] 1. The present invention adopts Kachanov's creep damage law and establishes an improved Burgers model, which can better describe the whole process of rock creep.

[0042] 2. The present invention uses the Lemaitre strain equivalence principle to establish the correlation between fractured rock mass and intact rock, and finds that the same creep model can be used to describe the creep process of fractured rock mass and intact rock, but the parameters are different.

[0043] 3. The present invention regards the cracks in the rock mass as a kind of damage to the intact rock. Combining the relationship between the cracked rock mass and the intact rock, the creep model of the cracked rock mass can be derived from the creep model of the intact rock. The rationality of the derived creep model of the cracked rock mass is verified by comparing the derived creep curve with the experimental creep curve.

[0044] 4. The fractured rock mass creep model derived by the present invention is convenient and simple, has wide applicability, and is more in line with actual working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is the graded loading creep curve diagram of all the samples in the examples of the present invention;

[0046] Figure 2 It is the single-stage loading creep curve diagram of all the samples in the examples of the present invention;

[0047] Figure 3 It is a diagram of the improved Burgers model in the example of the present invention;

[0048] Figure 4 It is the fitting curve diagram of N3β45° and N5β30° samples in the examples of the present invention;

[0049] Figure 5 It is a creep curve variation diagram caused by the variation of each creep model parameter under σ1=36MPa in the example of the present invention;

[0050] Figure 6 is a relationship diagram between the parameters η1 and σ1 in an example of the present invention;

[0051] Figure 7 It is a comparison diagram of the creep curve derived from the N3β30° and N5β0° samples and the sample curve in the examples of the present invention. DETAILED DESCRIPTION

[0052] Embodiment 1:

[0053] A method for deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material comprises the following steps:

[0054] S1, uniaxial compression creep tests are carried out on intact rock specimens and fractured rock specimens under different stresses to obtain creep curves of each specimen;

[0055] S2, the correlation between fractured rock mass and intact rock is established using Lemaitre strain equivalence principle, and Kachanov law is used to describe the time-dependent damage function D(t) of rock specimens in the accelerated creep stage;

[0056] S3, the attenuation and steady-state creep process of the specimen is described by the classic Burgers model constitutive equation, and the aging damage body E3,D(t) is introduced into the classic Burgers model constitutive equation to obtain the improved Burgers model constitutive equation reflecting the mechanical behavior of the entire creep process;

[0057] S4, the expression of the initial damage variable D0 is obtained based on the relationship between the unit volume strain energy of intact rock and fractured rock mass;

[0058] S5, selecting a suitable creep model for fitting according to the stress state of the sample, obtaining fitting parameters of the complete rock sample under different stresses, and simplifying the fitting parameters of the complete sample under different stresses;

[0059] S6, according to step 4, the initial damage variable D0 of different fractured specimens is calculated, and then combined with the simplified fitting parameters in step 5, it is substituted into the constitutive equation of the improved Burgers model to obtain the creep model of the fractured rock mass derived from the creep model of the intact rock.

[0060] Preferably, in step S1, the fractured specimen has prefabricated fractures with different geometric shapes compared to the intact specimen.

[0061] Preferably, in step S2, the Lemaitre strain equivalence principle equates the strain caused by the apparent stress applied to the damaged material to the strain caused by the equivalent stress acting on the undamaged material:

[0062]

[0063] Based on this, the relationship between intact rock and fractured rock mass can be expressed as:

[0064]

[0065] Where D is the damage variable.

[0066] Preferably, in step S2, the relationship between D(t) and σ1 is described as follows according to Kachanov's law:

[0067]

[0068] In the formula, C and n are rock material constants; σ1 is the stress on the rock;

[0069] Based on the above formula, according to the two boundary conditions D(t=0)=0 (when t=0, the material is not damaged), D(t=t F )=1(when t=t F , the material is completely damaged) and the rock damage evolution equation under creep state is derived as follows:

[0070]

[0071] In the formula, t F is the time of creep damage; take r=1 / (n+1).

[0072] Preferably, in step S3, the constitutive equation of the classic Burgers model is:

[0073]

[0074] Where, E1 is the instantaneous elastic modulus; E2 is the viscoelastic modulus; η1, η2 are the viscosity coefficients; σ L Long-term strength of rock mass.

[0075] Preferably, in step S3, the aging damaged body E3,D(t) is introduced into the constitutive equation of the classic Burgers model, and the constitutive equation of the improved Burgers model is obtained as follows:

[0076]

[0077] Where, E1 is the instantaneous elastic modulus; E2 is the viscoelastic modulus; η1, η2 are the viscosity coefficients; σ L Long-term strength of rock mass.

[0078] Preferably, in step S4, under uniaxial compression conditions, the elastic strain energy per unit volume of intact rock and rock mass containing fractures has the following relationship:

[0079]

[0080] In the formula, ΔU E is the unit elastic strain energy increased due to the existence of cracks, ΔU E The expression is:

[0081]

[0082] Combined ΔU E The final expression of the initial damage variable can be obtained by using the expression of

[0083]

[0084] Where U E and U E0 are the unit elastic strain energies of fractured rock and intact rock, respectively, and E0 is the elastic modulus of intact rock.

[0085] Preferably, in step S5, when the stress σ1≤σ L When the stress of the specimen is σ1>σ L When , the improved Burgers model is selected for fitting. The fitting values ​​of model parameters E1, E2, E3, r, η1, and η2 are obtained through fitting.

[0086] Preferably, in step S5, the method for simplifying the fitting parameters of the complete specimen under different stresses is: by controlling other parameters unchanged, changing the parameters to be simplified, and observing the changes in the creep curve; and selecting appropriate parameter values ​​according to the influence of the parameters on the creep process.

[0087] Preferably, in step S6, the creep model of the intact rock is used to derive the creep model of the fractured rock mass by substituting the initial damage variable D0 of the fractured rock sample and the simplified creep parameters of the intact rock into the constitutive equation of the improved Burgers model.

[0088] Embodiment 2:

[0089] The present invention includes seven steps: carrying out uniaxial compression creep tests on intact rock samples and fractured rock samples, establishing the relationship between intact rock and fractured rock mass and constructing a time-dependent damage function D(t), obtaining an improved constitutive equation of the classic Burgers model, calculating the expression of the initial damage variable D0, obtaining simplified fitting parameters of the intact sample, deriving a creep model of the fractured rock mass from the creep model of the intact rock, and model verification.

[0090] Step (1): Conduct uniaxial compression creep tests on intact rock specimens and fractured rock specimens;

[0091] The uniaxial compression creep tests were carried out on the complete and cracked rectangular rock specimens with a length of 100 mm, a width of 100 mm, and a height of 200 mm using single-stage loading and graded loading methods, and the creep curves of each specimen were obtained as shown in Figure 2. Figure 1 and Figure 2 As shown. The prefabricated cracks of the cracked specimen are evenly arranged in the middle of the specimen, the crack spacing is 20 mm, the crack length is 20 mm, and the opening is 0.5 mm; the number of cracks N and the inclination angle b are 1, 3, 5, 7 and 0°, 30°, 45°, 60°, 90° respectively. Nxβy is used to represent different specimens, such as Ⅰ represents a complete specimen; N5β30° represents a rock specimen with N=5 and β=30°. The initial axial pressure of the graded creep loading is set to the corresponding specimen s c 40% of the total stress, and the stress increase at each subsequent stage is corresponding to s c The axial stress of the single-stage creep loading is taken as the s of the corresponding specimen. L to c The middle two levels.

[0092] See also Figure 1 and Figure 2 , the creep curves of the intact specimen and the cracked specimen are consistent in the direction and trend of the curve. Under graded creep loading, in the first few levels with small axial pressure, all specimens did not experience the accelerated creep stage, and the creep curve only contained two stages: decay creep and steady-state creep; in the last two levels with large axial pressure, the specimens experienced accelerated creep and were destroyed, or the specimens were destroyed when loaded to the next level, and the creep curve contained three stages: decay creep, steady-state creep, and accelerated creep. Under single-stage creep loading, all specimens experienced the accelerated creep stage and were destroyed, and all creep curves contained three stages: decay creep, steady-state creep, and accelerated creep.

[0093] Step (2): Establish the relationship between intact rock and fractured rock mass and construct the time-dependent damage function D(t);

[0094] Lemaitre's strain equivalence principle equates the strain caused by the apparent stress applied to the damaged material to the strain caused by the equivalent stress acting on the undamaged material:

[0095]

[0096] Based on this, the relationship between intact rock and fractured rock mass can be expressed as:

[0097]

[0098] Where D is the damage variable.

[0099] According to Kachanov's law, the relationship between D(t) and σ1 is:

[0100]

[0101] In the formula, C and n are rock material constants; σ1 is the stress on the rock; Based on the above formula, according to the two boundary conditions D(t=0)=0 (when t=0, the material is not damaged), D(t=t F )=1(when t=t F , the material is completely damaged) and the rock damage evolution equation under creep state is derived as follows:

[0102]

[0103] In the formula, t F is the time of creep damage; take r=1 / (n+1).

[0104] Step (3): Obtain the improved constitutive equation of the classic Burgers model;

[0105] The Burgers model can better describe the mechanical properties of rock attenuation creep stage and stable creep stage, but lacks the description of the mechanical properties of accelerated creep stage. The present invention introduces the time-dependent damage body E3,D(t) into the constitutive equation of the classic Burgers model to establish an improved Burgers model that can reflect the mechanical behavior of the accelerated creep stage.

[0106] The constitutive equation of the classic Burgers model is:

[0107]

[0108] Where, E1 is the instantaneous elastic modulus; E2 is the viscoelastic modulus; η1, η2 are the viscosity coefficients; σ L Long-term strength of rock mass.

[0109] The time-dependent damaged body E3,D(t) in step 2 is introduced into the constitutive equation of the classic Burgers model to obtain the constitutive equation of the improved Burgers model (the schematic diagram of the model is shown in Figure 3 shown):

[0110]

[0111] Step (4): Calculate the expression of the initial damage variable D0;

[0112] The initial damage variable D0 represents the damage caused by the pre-existing cracks relative to the intact rock. It is determined by the geometric characteristics of the cracks, does not change with time, and is a fixed value for a specific specimen. Under uniaxial compression conditions, the elastic strain energy per unit volume of intact rock and rock with cracks has the following relationship:

[0113]

[0114] Where U E and U E0 are the unit elastic strain energies of fractured rock and intact rock, E0 is the elastic modulus of intact rock, ΔU E is the unit elastic strain energy increased due to the existence of cracks; and ΔU E The expression is:

[0115]

[0116] Combined ΔU E The final expression of the initial damage variable can be obtained by using the expression of

[0117]

[0118] For a rock mass with a single fracture under uniaxial compression, K Ⅰ and K Ⅱ It can be calculated as follows:

[0119]

[0120] For a rock mass containing multiple rows of fractures (of the same length and uniform spacing), K can be obtained by multiplying the coefficients f(a, s, N) with the corresponding values ​​for a single fracture. Ⅰ and K Ⅱ value.

[0121] Step (5): obtain simplified complete sample fitting parameters;

[0122] Based on Chen's loading method, Figure 1 The creep curves in the multi-stage loading creep test were converted into creep curves under different loading conditions. Then, the classic Burgers model and the improved Burgers model were used to fit these curves, and the fitting parameter values ​​and typical fitting curves were obtained as shown in Table 1 and Figure 4 shown.

[0123] Table 1: Model fitting parameters of the specimen

[0124]

[0125]

[0126] See Table 1 and Figure 4 It can be found that the theoretical curve fits the experimental data very well, and the fitting coefficient R 2 All of them are greater than 0.95, indicating that the improved Burgers model is applicable to all specimens, that is, the creep characteristics of all fractured specimens and intact specimens can be described by the same constitutive model, but with different parameters. In actual engineering, the stress state of rock mass at different locations is different. When applying the same creep model, it is difficult to use different parameter values ​​for each location. Therefore, it is necessary to simplify the model parameters of intact specimens under different stresses.

[0127] The elastic modulus E1 represents the instantaneous strain of the specimen (t = 0). E1 can be the secant modulus of the stress-strain curve of the uniaxially compressed rock specimen. The secant modulus reflects the overall stiffness of the rock and is generally represented by the slope of the line connecting the point corresponding to 50% of the uniaxial strength on the stress-strain curve and the origin of the coordinate system. Therefore, we take E1 as 50 As E1 value. Taking the intact sample under s1 = 36 MPa as an example, keeping other fitting parameters (Table 1) unchanged, changing parameters E2, E3, r, h1, h2, we get Figure 5 The creep curve is shown in the figure.

[0128] See also Figure 5 , the strain difference caused by the changes in E2, E3, r, and h2 is not large, and the influence on the creep curve is small. Therefore, we can take the average of the fitting values ​​of E2, E3, r, and h2 at each stress level as the model parameter value of E2, E3, r, and h2. As for h1, the larger the h1 value, the smaller the deformation rate of the rock in this stage, and the smaller the deformation in this stage.

[0129] Figure 6 shows the fitted values ​​of h1 for different values ​​of s1, see Figure 6 , the relationship between h1 and s1 can be described by the following exponential function:

[0130]

[0131] Step (6): Derive the creep model of the rock mass with fractures from the creep model of the intact rock; the steps of deriving the creep curve of the fractured rock mass from the creep curve of the intact rock are as follows: According to step 5, the simplified values ​​of the creep model parameters of the intact specimen under different stresses are obtained, and then combined with the D0 values ​​of different fractured specimens calculated in step 4, they are substituted into equations (5) and (6) to obtain the creep curve of the corresponding fractured specimen.

[0132] Step (7): Model verification;

[0133] Taking N3β30° and N5β0° samples as examples, the parameters of the complete sample are obtained through step six:

[0134] E1=7360MPa, E2=56323MPa, E3=45805MPa, r=0.144, h2=58057MPa·h, h1 of N3β30° and N5β0° samples are 3331125MPa·h, 3320969MPa·h, 3308158MPa·h, 3292001MPa·h, 3280793MPa·h, 3255349MPa·h and 3306027MPa·h, 3278641MPa·h, 3239531MPa·h, 3183679MPa·h, 3126596MPa·h, 3015350MPa·h respectively.

[0135] The calculation in step 4 yields D0 values ​​of N3β30° and N5β0° samples of 0.6637 and 0.4768, respectively.

[0136] Substituting all parameters into equations (5) and (6), we can obtain the comparison between the derived creep curve and the test curve: Figure 7 shown.

[0137] See also Figure 7 , Figure 7 (a) and (c) are such that σ1≤σ L In the case of , the curve has no accelerated creep stage; (b) and (d) are σ1>σ L In the case of , the curve contains an accelerated creep stage. It can be seen that all theoretical derivation curves and test curves are consistent in morphology, and the curve fit is also high, indicating that the method of deriving the creep model of fractured rock mass from the creep model of intact rock in this patent is feasible. The derived fractured rock mass creep model is applicable to rock masses with different stresses and different fracture geometric characteristics, and can also well reflect the three stages of the entire process of uniaxial compression creep of rocks.

Claims

1. A method for deriving a creep model of jointed rock and soil materials based on a creep model of complete rock and soil materials. It is characterized in that The following steps are involved: S1, uniaxial compression creep tests are carried out on intact rock specimens and fractured rock specimens under different stresses to obtain creep curves of each specimen; S2, the correlation between fractured rock mass and intact rock is established using Lemaitre strain equivalence principle, and Kachanov law is used to describe the time-dependent damage function D(t) of rock specimens in the accelerated creep stage; S3, the classic Burgers model constitutive equation is used to describe the decay and steady-state creep process of the sample, and the aging damage volume E 3 ,D(t) introduces the classic Burgers model constitutive equation to obtain the improved Burgers model constitutive equation reflecting the mechanical behavior of the entire creep process; S4, the initial damage variable D is obtained based on the relationship between the unit volume strain energy of intact rock and fractured rock mass. 0 Expression of S5, selecting a suitable creep model for fitting according to the stress state of the sample, obtaining fitting parameters of the complete rock sample under different stresses, and simplifying the fitting parameters of the complete sample under different stresses; S6, calculate the initial damage variable D of different crack specimens according to step 4 0 , combined with the simplified fitting parameters in step five, and substituted into the constitutive equation of the improved Burgers model, we can obtain the creep model of the fractured rock mass derived from the creep model of the intact rock.

2. A method for deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material according to claim 1, It is characterized in that In step S1, the cracked specimen has prefabricated cracks with different geometric shapes compared to the intact specimen.

3. A method for deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material according to claim 2, It is characterized in that In step S2, the Lemaitre strain equivalence principle equates the strain caused by the apparent stress applied to the damaged material to the strain caused by the equivalent stress acting on the undamaged material: Based on this, the relationship between intact rock and fractured rock mass can be expressed as: Where D is the damage variable.

4. A method for deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material according to claim 3, It is characterized in that In step S2, the Kachanov law is used to describe the relationship between D(t) and σ 1 The relationship is: Where, C and n are rock material constants; σ 1 The stress on the rock; Based on the above formula, according to the two boundary conditions D(t=0)=0 (when t=0, the material is not damaged), D(t=t F )=1(when t=t F , the material is completely damaged) and the rock damage evolution equation under creep state is derived as follows: Where, t F is the time of creep damage; take r=1 / (n+1).

5. A method for deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material according to claim 4, It is characterized in that In step S3, the constitutive equation of the classic Burgers model is: In the formula, E 1 is the instantaneous elastic modulus; E 2 is the viscoelastic modulus; η 1 , η 2 is the viscosity coefficient; σ L Long-term strength of rock mass.

6. A method for deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material according to claim 5, It is characterized in that In step S3, the aging damaged body E 3 ,D(t) introduces the constitutive equation of the classic Burgers model, and the constitutive equation of the improved Burgers model is obtained as follows: In the formula, E 1 is the instantaneous elastic modulus; E 2 is the viscoelastic modulus; η 1 , η 2 is the viscosity coefficient; σ L Long-term strength of rock mass.

7. The method of deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material according to claim 1, It is characterized in that In step S4, under uniaxial compression conditions, the elastic strain energy per unit volume of intact rock and rock mass containing fractures has the following relationship: In the formula, ΔU E is the unit elastic strain energy increased due to the existence of cracks, ΔU E The expression is: Combined ΔU E The final expression of the initial damage variable can be obtained by using the expression of Where U E and U E0 are the unit elastic strain energies of fractured rock mass and intact rock, E 0 is the elastic modulus of intact rock.

8. The method of deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material according to claim 1, It is characterized in that In step S5, when the stress σ 1 ≤σ L When the stress σ 1 >σ L When the improved Burgers model is used for fitting, the model parameters E 1 、E 2 、E 3 , r, η 1 , η 2 The fitted value of .

9. A method for deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material according to claim 8, It is characterized in that In step S5, the method for simplifying the fitting parameters of the complete specimen under different stresses is: by controlling other parameters unchanged, changing the parameters to be simplified, and observing the changes in the creep curve; and selecting appropriate parameter values ​​according to the influence of the parameters on the creep process.

10. A method for deriving a creep model of a jointed rock mass material based on a creep model of a complete rock mass material according to claim 9, It is characterized in that In step S6, the creep model of the intact rock is used to derive the creep model of the fractured rock mass by: 0 The simplified creep parameters of the intact rock are substituted into the constitutive equation of the improved Burgers model.

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