Method and system for obtaining mechanical parameters of rock mass joint unit

Abstract

The application belongs to the technical field of geotechnical mechanics, and particularly discloses a method and system for obtaining mechanical parameters of a rock mass joint unit. The method comprises the following steps: obtaining macro mechanical parameters of complete rock based on indoor rock basic mechanical test; dividing rock mass grades of engineering rock mass according to a rock mass quality classification standard to obtain equivalent rock mass mechanical parameters; deducing an elastic-plastic stiffness matrix of the joint unit according to Mohr-Coulomb criterion and associated flow rule; and calculating the mechanical parameters of the joint unit and verifying the rationality of the mechanical parameters of the joint unit according to the homogenization theory and the limit strain theory. The application processes the structural surface into a soft interlayer with a certain thickness based on the idea of the equivalent continuous model, divides the rock mass into elastic rock units and elastic-plastic joint units, comprehensively obtains the mechanical properties of the joint unit through analysis of the entire joint rock mass unit, and can meet the engineering calculation accuracy and facilitate direct application of indoor test data.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of rock-soil mechanics, and more particularly, to a method and system for obtaining mechanical parameters of a rock mass joint unit. BACKGROUND

[0002] Rock mass is a geological body that has experienced a long history of rock formation, and its interior is usually distributed with a large number of fractures and joint fissures. These micro-fissures are numerous, small in size, and high in cutting degree, which directly affect the mechanical properties and deformation characteristics of the rock mass. However, due to the extremely large number of joint fissures, it is not feasible to simulate them one by one. Therefore, how to accurately and efficiently simulate the structure of the rock mass with numerous joint fissures has become a problem that needs to be solved in the field of rock mass engineering.

[0003] Currently, there are two main strategies for solving the equivalent rock mass structure. The first strategy is based on the understanding of the widespread defects in rock-soil materials, and the rock mass characterization unit method is established by analyzing the influence of discontinuous structure on the overall mechanical behavior of the material (Zhou, C. B., & Yu, S. D. On rock mass characterization unit volume REV- a basic problem of rock mass mechanical parameter selection [J]. Chinese Journal of Geotechnical Engineering, 1999, 7(4): 332-336.). This method divides the rock mass into grades through the rock mass quality classification standards such as BQ, GSI and RQD index, obtains the mechanical parameters of the rock mass, and determines the rock mass characterization unit volume (REV) through numerical simulation analysis. The mechanical parameters of the rock mass characterization unit are taken as the mechanical parameters of the engineering scale rock mass (Kulatilake, P. H. S. W. Estimating elastic constants and strength of discontinuous rock [J]. Journal of geotechnical engineering, 1985, 111(7): 847-864. He, M. C., Xue, T. H., & Peng, Y. F. Research on determination method of engineering rock mass mechanical parameters [J]. Chinese Journal of Rock Mechanics and Engineering, 2001(02): 225-229.). In addition, Chinese patent CN113946958A discloses a method for obtaining rock mass characterization unit REV based on discrete fracture network method, which can reasonably reflect the macroscopic mechanical behavior of general fractured rock mass, and is the popular method in the engineering field. However, due to the size effect, the indoor test data of the rock mass cannot be used as the main basis for parameter selection. The second strategy regards the rock mass as a two-phase structure composed of intact rock and structural plane. In this method, both the rock unit and the structural plane unit are regarded as isotropic bodies, but the rock mass unit composed of the two is an anisotropic body. This method unifies the two failure modes of rock failure and joint failure along the joint surface through the strength equivalence principle, and obtains the mechanical parameters of the overall rock mass. The above strength equivalence method is the current frontier of academic research. In this method, the rock mechanical parameters are obtained through indoor mechanical tests, and the mechanical parameters of the joint unit become the key to accurately characterize the mechanical properties and failure characteristics of the rock mass structure.

[0004] In summary, the current solving method for equivalent rock mass structure still has some defects, mainly reflected in the following aspects: (1) Joints are widely distributed in natural rock mass, and the analyzed medium has discrete uncertainty. If all are treated as joint units, it will bring great difficulty to numerical modeling and calculation; (2) Due to the size effect, the REV value of the rock mass is usually large or even non-existent, and the test results of the laboratory sample cannot be directly used as the basis for the mechanical parameter selection of the rock mass characterization unit.

[0005] Based on the above defects and deficiencies, the technical field urgently needs to propose a new method for obtaining mechanical parameters of rock mass joint unit to overcome the discrete uncertainty of the medium and the inaccuracy of the value based on the test results in the prior art. SUMMARY

[0006] In view of the above defects or improvement needs of the prior art, the present application provides a method and system for obtaining mechanical parameters of rock mass joint unit, which is based on the idea of equivalent continuous model, treats the structural plane as a soft interlayer with a certain thickness, divides the rock mass into elastic rock units and elastic-plastic joint units, and comprehensively obtains the mechanical properties of the joint units through analysis of the entire joint rock mass unit. This method combines indoor mechanical tests and rock mass classification, which can meet the engineering calculation accuracy and facilitate the direct application of indoor test data.

[0007] To achieve the above object, according to one aspect of the present application, a method for obtaining mechanical parameters of rock mass joint unit is provided, comprising the following steps:

[0008] S1 obtaining macro mechanical parameters of complete rock based on indoor rock basic mechanical test;

[0009] S2 obtaining equivalent rock mass mechanical parameters by classifying the engineering rock mass according to rock mass classification standard;

[0010] S3 deriving the elastic-plastic stiffness matrix of the joint unit according to Mohr-Coulomb criterion and associated flow rule;

[0011] S4 calculating the strength parameters of the joint unit according to the homogenization theory, substituting the mechanical parameters of complete rock, the equivalent rock mass mechanical parameters and the elastic-plastic stiffness matrix of the joint unit, and calculating the limit strain of the equivalent rock mass based on the limit strain theory and the equivalent rock mass mechanical parameters;

[0012] S5 calculating the fracture energy of the joint unit according to the limit strain of the equivalent rock mass and the strength parameters of the joint unit, and determining the mechanical parameters of the joint unit.

[0013] As a further preferred, in step S1, the indoor rock basic mechanical test includes rock uniaxial compression and rock Brazilian splitting test, the elastic modulus E r and Poisson's ratio v r of complete rock are obtained according to the rock uniaxial compression test; and the tensile strength f t r of complete rock is obtained according to the rock Brazilian splitting test.

[0014] As a further preferred, in step S2, the equivalent rock mass mechanical parameters include elastic modulus E m , Poisson's ratio v m , cohesive force cm , internal friction angle and tensile strength f t m .

[0015] As a further preferred, step S3 comprises the following steps:

[0016] S31 constructing yield function f and first material parameter m(κ) and second material parameter σ c (κ) expression, selecting Mohr-Coulomb criterion as the yield criterion of joint element, constructing yield function:

[0017] f(σ1,σ3,κ)=m(κ)σ1-σ3-σ c (κ)=0

[0018] In the formula, σ1 and σ3 are the maximum principal stress and the minimum principal stress of the material respectively, and the internal variable κ represents the hardening degree of the material;

[0019] S32 constructing the elastoplastic stiffness matrix of the joint element, wherein the plastic deformation adopts the flow rule associated with the yield surface, and the calculation model of the elastoplastic stiffness matrix [K ep ] of the joint element is as follows:

[0020]

[0021] In the formula, [K e ] is the elastic stiffness matrix of the joint element, R is the hardening modulus, and σ is the vector representation of the stress of the joint element.

[0022] As a further preferred, step S4 comprises the following steps:

[0023] S41 solving the stiffness of the joint element: according to the stiffness equivalence principle of continuous medium, the normal stiffness K N and the tangential stiffness K S of the joint element are solved;

[0024] S42 solving the tensile strength and shear strength of the joint element: according to the requirement of homogenization theory, the yield points of the joint element and the equivalent rock element are consistent, and the calculation formula of the tensile strength f t , initial cohesion c0 and initial internal friction of the joint element are constructed.

[0025] As a further preferred, the calculation formula of the normal stiffness K N and the tangential stiffness K S of the joint element is as follows:

[0026]

[0027]

[0028] wherein, h is the thickness of the equivalent rock element, E r and v r are the elastic modulus and Poisson's ratio of the intact rock, respectively, E m and v m are the elastic modulus and Poisson's ratio of the engineering rock mass, respectively;

[0029] As a further preferred, the tensile strength f t , the initial cohesion c0and the initial internal friction of the joint element are calculated by the following formulas, respectively:

[0030] f t = f t m

[0031]

[0032]

[0033] wherein, f t m , c m and are the tensile strength, the cohesion and the internal friction angle of the equivalent rock element, respectively, is the shear strain of the equivalent rock at the initial yield point.

[0034] As a further preferred, in the step S4, the calculating the limit strain of the equivalent rock mass comprises: according to the limit strain theory, solving the limit strain of the equivalent rock element under the uniaxial compression condition by using the numerical limit analysis method, and

[0035]

[0036]

[0037]

[0038] wherein, is the lateral strain of the equivalent rock element under the uniaxial compression condition, c m is the cohesion of the equivalent rock element, is the internal friction angle of the equivalent rock element, E m and v m are the elastic modulus and Poisson's ratio of the equivalent rock, respectively.

[0039] As a further preferred, in the step S5, the calculating the I-type fracture energy GI and type II breaking energy G II :

[0040]

[0041]

[0042] where f s and f s are the initial shear strength and the residual shear strength of the joint element respectively; Δε and Δγ are the normal cumulative strain and the tangential cumulative strain of the joint element from the initial yield point to the failure point respectively.

[0043] As a further preferred, it further comprises: based on the finite-discrete element coupling software / program, numerical simulation of uniaxial compression and Brazilian splitting test, verifying the applicability and rationality of the joint element mechanical parameter value.

[0044] According to another aspect of the present application, there is also provided a rock mass joint element mechanical parameter value system for realizing the above method.

[0045] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages:

[0046] 1. The present application is based on the idea of equivalent continuous model, which processes the structural plane in the engineering rock mass as a soft interlayer with a certain thickness, divides the equivalent rock mass element into an elastic rock element and a joint element with elastic-plasticity, so that the anisotropic equivalent rock mass element can be divided into two isotropic elements that interact with each other. The established equivalent rock mass model not only considers the influence of joints on the mechanical properties of rock mass, but also can be regarded as a continuum in the macroscopic aspect, thereby overcoming the problems of modeling difficulty and low computational efficiency in simulating general jointed fractured rock mass in the traditional method.

[0047] 2. The present application considers the influence of joints on the mechanical properties of rock mass, adopts Mohr-Coulomb criterion and the associated flow rule to describe the elastic-plastic deformation of the joint element, and based on the homogenization theory and the limit strain theory, the calculation formula of the mechanical parameters of the joint element is derived through comprehensive analysis of the entire jointed rock mass element. The derivation process comprehensively considers the indoor mechanical test and rock mass quality classification, thereby overcoming the inaccuracy of directly using the results of indoor mechanical test in the traditional method, and can more accurately reflect the macroscopic mechanical behavior of jointed rock mass.

[0048] 3. The derived joint unit mechanical parameter value formula of the application has clear physical meaning of calculation parameters, which can be obtained by rock mechanics test results and rock mass quality classification standard, and the value results can be verified by finite-discrete element coupling software / program, so that the method is simple, convenient, practical and easy to popularize, and is an equivalent parameter analysis method of jointed rock mass which can meet the engineering calculation precision and directly apply the laboratory test data. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is a flow chart of a rock mass joint unit mechanical parameter value method according to an embodiment of the application;

[0050] Figure 2 (a) in the figure is a schematic diagram of a uniaxial compression test in a laboratory, Figure 2 (b) in the figure is a schematic diagram of a Brazilian split test in a laboratory;

[0051] Figure 3 (a) in the figure is a trend graph of a joint unit cohesion parameter according to the method of the application with respect to κ, Figure 3 (b) in the figure is a trend graph of a joint unit internal friction angle parameter according to the method of the application with respect to κ;

[0052] Figure 4 (a) in the figure is a joint unit normal stress-strain curve graph, Figure 4 (b) in the figure is a joint unit tangential stress-strain curve graph;

[0053] Figure 5 (a) in the figure is a FDEM-uniaxial compression numerical simulation model according to the application, Figure 5 (b) in the figure is a FDEM-Brazilian split numerical simulation model according to the application;

[0054] Figure 6 (a) in the figure is a finite-discrete element stress-strain curve of a uniaxial compression numerical simulation according to the application, Figure 6 (b) in the figure is a finite element stress-strain curve of a Brazilian split numerical simulation according to the application. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the application clearer and more apparent, the application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application. In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as they do not conflict with each other.

[0056] As Figure 1As shown, the method for obtaining the mechanical parameters of a rock mass joint unit provided by the embodiment of the application comprises the following steps:

[0057] Step 1: obtaining the macro mechanical parameters of the complete rock based on the indoor rock basic mechanical test. That is, obtaining the macro mechanical parameters of the complete rock based on the indoor rock basic mechanical test. Specifically, in the step 1, the rock mechanical test comprises the uniaxial compression and the Brazilian splitting test, such as Figure 2 As shown, the elastic modulus E of the complete rock is obtained according to the uniaxial compression test of the rock r and the Poisson's ratio v r ; the tensile strength f of the complete rock is obtained according to the Brazilian splitting test of the rock t r In the application, the uniaxial compression and the Brazilian splitting test both belong to the prior art, and the conventional uniaxial compression and the Brazilian splitting test can meet the requirement of obtaining the rock parameters of the application. The specific structure and method are not described herein.

[0058] Step 2: obtaining the macro mechanical parameters of the engineering rock mass based on the rock mass quality classification standard. That is, obtaining the equivalent rock mass mechanical parameters according to the rock mass grade division of the engineering rock mass according to the rock mass quality classification standard. Specifically, the rock mass quality grade division standard comprises the national standard BQ, GSI and RQD index, etc. According to the rock mass quality classification standard, the rock mass in the engineering is divided into grades, and the elastic modulus E m , the Poisson's ratio v m , the cohesive force c m , the internal friction angle and the tensile strength f t of the engineering rock mass are obtained. m .

[0059] Step 3: deriving the elastoplastic stiffness matrix of the joint unit based on the Mohr-Coulomb criterion and the associated flow rule. Specifically, the elastoplastic stiffness matrix of the joint unit can be solved by the following steps:

[0060] Step 3.1: constructing the yield function f and the expressions of the first material parameter m(κ) and the second material parameter σ c (κ): selecting the Mohr-Coulomb criterion as the yield criterion of the joint unit, the yield function f(σ1,σ3,κ) can be expressed as:

[0061] f(σ1,σ3,κ)=m(κ)σ1-σ3-σ c (κ)=0 (1)

[0062] Where σ1 and σ3 are the maximum and minimum principal stresses of the material, respectively; the internal variable κ represents the degree of hardening of the material, which determines how the yield surface of the hardened / softened material will change, and its value is usually related to the plastic strain; the first material parameter m(κ) is the ratio of the compressive strength to the tensile strength; the second material parameter σ c (κ) characterizes the unconfined compressive strength. The first material parameter m(κ) and the second material parameter σ c (κ) and the expression of the internal variable κ is:

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] Among them, c(κ) and are the cohesion and internal friction angle of the jointed rock mass, respectively. In the elastic-plastic stage, they are linear functions of the internal variable κ, that is, they decrease as the internal variable κ increases, but the degree of decrease is different, such as Figure 3 As shown. c0 and are the initial cohesion and initial internal friction angle of the joint unit, and κ r are the internal friction angle and internal variable when the unit is completely destroyed; and dε p are the equivalent plastic strain and plastic strain increment, respectively.

[0069] Step 3.2, construct the stiffness matrix K of the joint unit: Plastic deformation adopts the flow law associated with the yield surface, then the elastic-plastic stiffness matrix of the joint unit [K ep ] is:

[0070]

[0071]

[0072]

[0073] Among them, [K e ] is the elastic stiffness matrix of the joint element, K N and K S are the normal stiffness and tangential stiffness coefficients of the joint element; R is the hardening modulus, which is 0 at the yield point; σ is the vector representation of the stress of the joint element.

[0074] Step 4: Calculate the mechanical parameters of the joint unit based on the homogenization theory and the ultimate strain theory. In the present invention, the homogenization theory is to use the homogenization criterion as well as stress balance and motion constraints to combine units with two different mechanical properties into a new unit. According to the homogenization theory, the relative displacement between the joint and the rock occurs within the joint unit, and the two interfaces remain completely bonded. The homogenization theory requires that the yield points of the joint unit and the equivalent rock unit remain consistent, that is, when the joint unit reaches the yield strain, the stress state of the joint unit and the rock unit at that moment both satisfy the yield function. The ultimate strain theory uses the ultimate strain under unidirectional stress as the criterion for the failure of geotechnical materials under unidirectional stress. The ultimate strain theory believes that when the material just reaches yield, it is the initial yield and has an elastic ultimate strain. As the plasticity develops, the material fails and the strain reaches the ultimate strain. The equivalent rock unit and joint unit of the present invention adopt the elastic-plastic constitutive law. Therefore, it is feasible to use the ultimate strain theory to calculate the ultimate strain of the rock unit and the joint unit.

[0075] In step 4, the rock unit adopts elastic constitutive model and the rock mass unit adopts perfect elastic-plastic constitutive model. The mechanical parameters of the joint unit can be calculated as follows:

[0076] Step 4.1, solve the joint unit stiffness: According to the stiffness equivalence principle of continuous media, the normal stiffness K of the joint unit N and tangential stiffness K S The calculation formula is as follows:

[0077]

[0078]

[0079] Where:

[0080]

[0081]

[0082]

[0083]

[0084] Where h is the thickness of the equivalent rock mass unit; E r and v r are the elastic modulus and Poisson's ratio of intact rock, respectively, and their values ​​are based on the initial straight line segment of the stress-strain curve of the indoor uniaxial compression test; E m and v m are the elastic modulus and Poisson's ratio of the equivalent rock mass, respectively, and their values ​​are based on the rock mass quality classification standard.

[0085] Step 4.2, solving the tensile strength and shear strength of the joint element: according to the requirement of the homogenization theory, the yield points of the joint element and the equivalent rock mass element are consistent, then the tensile strength f t , the initial cohesion c0and the initial internal friction angle of the joint element are calculated as follows:

[0086] f t = f t m (16)

[0087]

[0088]

[0089] In the formula:

[0090]

[0091]

[0092] wherein, f t m , c m and are the tensile strength, the cohesion and the internal friction angle of the equivalent rock mass element, and the values are taken according to the rock mass quality classification standard; is the shear strain of the equivalent rock mass at the initial yield point, and the specific value is detailed in step 4.3.

[0093] Step 4.3, solving the fracture energy of the joint element: Figure 4 is the stress-strain curve of the joint element, and the area surrounded by the curve after the yield stage is the fracture energy of the element, then the calculation formula of the I-type fracture energy G I and the II-type fracture energy G II of the joint element are as follows:

[0094]

[0095]

[0096] wherein, f s and f s ' are the initial shear strength and the residual shear strength of the joint element respectively; Δε and Δγ are the normal cumulative strain and the tangential cumulative strain of the joint element from the initial yield point to the failure point respectively. The calculation formula of Δε and Δγ is as follows:

[0097]

[0098]

[0099] wherein, t is the thickness of the joint element; and are the tensile strain at the initial yield point and the complete failure point when the equivalent rock mass unit is stretched; and are the shear strain at the initial yield point and the complete failure point when the equivalent rock mass unit is sheared. According to the limit strain theory, and The numerical limit analysis method can be used to solve the relationship as follows:

[0100]

[0101]

[0102]

[0103] wherein, is the lateral strain of the equivalent rock mass unit under the condition of uniaxial compression.

[0104] Step 5: Based on the finite-discrete element coupling software, the uniaxial compression and the Brazilian splitting test are simulated, and the applicability and rationality of the method for determining the mechanical parameters of the joint unit are verified. In the step 5, the finite-discrete element software is used, the complete rock mechanics parameters in the step 1 are taken as the input parameters of the solid element, and the mechanical parameters of the joint calculated in the steps 3-4 are taken as the input parameters of the joint unit, and the uniaxial compression and the Brazilian splitting are simulated. The numerical model is shown in (a) and (b) of FIG. 8, and the stress-strain curve results of the model are shown in (a) and (b) of FIG. 9. By comparing the finite-discrete element simulation results and the engineering rock mass quality classification results, the applicability and rationality of the method for determining the mechanical parameters of the rock joint unit are verified. Figure 5 Figure 6

[0105] Those skilled in the art will readily understand that the above description is only preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.​​

Claims

1. A method for determining the mechanical parameters of a rock mass joint unit, characterized in that: The following steps are involved: S1 obtains complete rock mechanical parameters based on indoor basic rock mechanical tests; S2 classifies the engineering rock mass according to the rock mass quality classification standard and obtains the equivalent rock mass mechanical parameters; S3 derives the elastic-plastic stiffness matrix of the joint element according to the Mohr-Coulomb criterion and the associated flow law; S4 calculates the joint unit strength parameters by substituting the complete rock mechanics parameters, equivalent rock mass mechanics parameters and the elastic-plastic stiffness matrix of the joint unit according to the homogenization theory. At the same time, the equivalent rock mass limit strain is calculated based on the limit strain theory and the equivalent rock mass mechanics parameters. S5: calculating the fracture energy of the joint unit according to the equivalent rock mass ultimate strain and the strength parameter of the joint unit, and determining the mechanical parameters of the joint unit based on the energy; Step S3 includes the following steps: S31 constructs the yield function f and the first material parameter m(κ) and the second material parameter σ c (κ) expression, select the Mohr-Coulomb criterion as the yield criterion of the joint element, and construct the yield function: f(σ1,σ3,κ)=m(κ)σ1-σ3-σ c (k)=0 Where σ1 and σ3 are the maximum and minimum principal stresses of the material, respectively, and the internal variable κ represents the hardening degree of the material; S32 constructs the elastic-plastic stiffness matrix of the joint unit, wherein the plastic deformation adopts the flow law associated with the yield surface, and the elastic-plastic stiffness matrix of the joint unit [K ep The calculation model of ] is as follows: In the formula, [K e ] is the elastic stiffness matrix of the joint element, R is the hardening modulus, and σ is the vector representation of the stress of the joint element; Step S4 includes the following steps: S41 solves the joint unit stiffness: According to the stiffness equivalence principle of continuous media, solve the normal stiffness K of the joint unit N and tangential stiffness K S ; S42 solves the tensile strength and shear strength of the joint unit: According to the requirements of the homogenization theory, the yield point of the joint unit and the equivalent rock unit are kept consistent, and the tensile strength f of the joint unit is constructed. t , initial cohesion c0 and initial internal friction The calculation formula of .

2. The method for determining the mechanical parameters of a rock mass joint unit according to claim 1, wherein: In step S1, the indoor rock basic mechanical test includes rock uniaxial compression and rock Brazilian splitting test, and the elastic modulus E of the intact rock is obtained according to the rock uniaxial compression test. r and Poisson's ratio v r ; Obtain the tensile strength of intact rock based on the Brazilian splitting test 3. The method for determining the mechanical parameters of a rock mass joint unit according to claim 1, wherein: In step S2, the equivalent rock mass mechanical parameters include elastic modulus E m , Poisson's ratio v m , cohesion c m , internal friction angle and tensile strength 4. The method for determining the mechanical parameters of a rock mass joint unit according to claim 1, wherein: The normal stiffness K of the joint element N and tangential stiffness K S The calculation formula is as follows: Where, h is the thickness of the equivalent rock mass unit, E r and v r are the elastic modulus and Poisson’s ratio of intact rock, E m and v m are the elastic modulus and Poisson’s ratio of the equivalent rock mass, respectively; The tensile strength f of the joint unit t , initial cohesion c0 and initial internal friction The calculation formulas are: Where, c m and are the tensile strength, cohesion and internal friction angle of the equivalent rock mass unit, is the shear strain of the equivalent rock mass at the initial yield point.

5. The method for obtaining mechanical parameters of rock mass joint units according to claim 1, characterized in that: In step S5, the fracture energy of the joint unit includes the mode I fracture energy G I and mode II fracture energy G II , and its calculation formula is: Where, f s and f s ' are the initial shear strength and residual shear strength of the joint unit, respectively; Δε and Δγ are the normal cumulative strain and tangential cumulative strain of the joint unit from the initial yield point to the failure point, respectively.

6. A method for obtaining mechanical parameters of rock mass joint units according to any one of claims 1 to 5, characterized in that: Also includes: Based on the finite-discrete element coupling software, numerical simulations of uniaxial compression and Brazilian splitting tests were carried out to verify the applicability and rationality of the mechanical parameter values ​​of the joint unit.

7. A system for obtaining mechanical parameters of rock mass joint units, characterized in that: A method for obtaining mechanical parameters of a rock joint unit according to any one of claims 1 to 6.

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