Quantitative identification method for anisotropic compression-shear failure of rock under true three-dimensional stress

Abstract

The present application relates to a kind of rock anisotropy compression-shear failure quantitative identification method under true three-dimensional stress, method includes: preparing rock true three-dimensional compression-shear test sample;Rock compression-shear test under true three-dimensional stress state is carried out;Obtain rock compression-shear full stress-strain relationship curve under true three-dimensional stress state;Determine rock compression-shear characteristic strength parameters under true three-dimensional stress state;Divide rock compression-shear deformation development stage under true three-dimensional stress stress state;Determine the deformation ratio change of intermediate principal stress direction and minor principal stress direction in the whole process of deviatoric stress loading;Quantitative distinguish rock anisotropy compression-shear failure mode under true three-dimensional stress state.The method can quantitatively distinguish rock anisotropy compression-shear failure mode under true three-dimensional stress.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics, and in particular to a method for quantitative identification of anisotropic compressive-shear failure of rocks under true three-dimensional stress. Background Technology

[0002] In recent years, the number of deep underground projects has been increasing year by year, and more and more major deep underground projects have been included in national development strategic plans. These include deep-buried tunnel projects, underground nuclear waste disposal projects, deep geothermal extraction projects, deep oil and gas extraction projects, and underground carbon dioxide storage projects. Therefore, the rational design, safe construction, and stable operation of these major deep underground projects are of great significance to ensuring national economic development. For deep underground projects, the surrounding rock is often under a true three-dimensional stress state. Affected by excavation unloading and high ground stress at depth, the surrounding rock under this true three-dimensional stress state will experience varying degrees of cracking, which can, in severe cases, induce rock bursts, large deformations, and other engineering accidents. This not only threatens the personal safety of workers but also causes huge economic losses.

[0003] To explore the fracture characteristics of surrounding rock under true three-dimensional stress, researchers conducted extensive true triaxial compression-shear tests on various isotropic and anisotropic rocks, including granite, sandstone, and slate. They discovered that rocks often exhibit anisotropic compression-shear failure modes under true three-dimensional stress, primarily two: the failure surface's normal direction is perpendicular to the direction of the intermediate principal stress, and the failure surface's normal direction is perpendicular to the direction of the minimum principal stress. Quantitatively classifying these two typical failure modes is crucial for accurately identifying the location of fractures in deep underground engineering and effectively controlling fractures. It is also key to establishing a theory of rock fracture under true three-dimensional stress and corresponding numerical calculation methods.

[0004] At present, there is a lack of quantitative identification methods for anisotropic compression-shear failure modes of rocks under true three-dimensional stress. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for quantitative identification of anisotropic compression-shear failure of rocks under true three-dimensional stress.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, embodiments of the present invention provide a method for quantitative identification of anisotropic compressive-shear failure of rocks under true three-dimensional stress, comprising:

[0010] S10. Obtain a test specimen for rock compression-shear testing and conduct a rock compression-shear test on the test specimen.

[0011] S20. Based on rock compression-shear tests, the full stress-strain relationship curve of rock compression-shear under true three-dimensional stress state was obtained;

[0012] S30. Analyze the full stress-strain relationship curve of the rock under compression and shear to obtain the characteristic strength parameters of rock under true three-dimensional stress and the anisotropic compression and shear failure mode of rock under true three-dimensional stress.

[0013] Optionally, S10 includes:

[0014] Prepare true three-dimensional rock compression-shear test specimens and conduct true three-dimensional rock compression-shear tests under stress conditions;

[0015] The test specimen is a cube with the same length L and width W, and the ratio of height H to length is 2:1.

[0016] Optionally, S30 includes:

[0017] S31. Analyze the full stress-strain relationship curve of rock under true three-dimensional stress state;

[0018] S32. Obtain the characteristic strength parameters of rock compression and shear under true three-dimensional stress state;

[0019] S33. Divide the development stages of rock compression-shear deformation under true three-dimensional stress state;

[0020] S34. Determine the deformation ratio changes in the direction of the intermediate principal stress and the direction of the minor principal stress throughout the entire process of deviatoric stress loading; wherein, the true three-dimensional stress state is σ1>σ2>σ3, where σ1 is the maximum principal stress, σ2 is the intermediate principal stress, and σ3 is the minimum principal stress;

[0021] S35. Quantitatively distinguish the anisotropic compression-shear failure modes of rocks under true three-dimensional stress state.

[0022] Optionally, the true three-dimensional stress state rock compression-shear test covers rock compression-shear tests with stress states conforming to σ1>σ2>σ3;

[0023] The rock compression-shear full stress-strain relationship curve is: the curve of the strain relationship between the deviatoric stress and the three principal stress directions obtained throughout the entire process from the start of loading to the failure of the specimen or the appearance of residual strength;

[0024] The characteristic strength parameters of rock compression and shear under true three-dimensional stress state include: crack initiation stress, damage stress, peak stress, and residual stress.

[0025] Optionally, the rock compression-shear deformation development stages under true three-dimensional stress stress state include: pre-peak deformation stage and post-peak deformation stage;

[0026] The pre-peak deformation stage includes: linear elastic deformation stage and crack unstable propagation stage;

[0027] The post-peak deformation stage includes: stress drop stage and residual stage.

[0028] Optionally, S34 includes:

[0029] The deformation ratio between the intermediate principal stress direction and the minor principal stress direction throughout the entire process of deviatoric stress loading is:

[0030]

[0031] Where ξ is the deformation ratio between the intermediate principal stress direction and the minor principal stress direction. D2 and D3 are the deformations measured in the intermediate principal stress direction and the minor principal stress direction, respectively, under the same deviatoric stress level. ξ is a function of deviatoric stress.

[0032] Optionally, the anisotropic compression-shear failure mode of rock under true three-dimensional stress state refers to: failure in which the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress, and failure in which the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress.

[0033] Optionally, S35 includes:

[0034] The failure mode of rock under true three-dimensional stress state is identified by the change of ξ with deviatoric stress in the pre-peak stage.

[0035] When the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress, formulas (1) and (2) are both valid; otherwise, the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress.

[0036]

[0037] ξ≥1,σ cd <σ1-σ3<σ p (2)

[0038] Where dξ is the increment of ξ caused by the change in deviatoric stress, σ ci σ cd σ p These are the initiation stress, damage stress, and peak stress, respectively, and q is the deviatoric stress, which is the difference between the maximum principal stress σ1 and the minimum principal stress σ3.

[0039] Optionally, S35 includes:

[0040] The anisotropic compression-shear failure mode of rock under true three-dimensional stress state is quantitatively identified by the change of ξ with deviatoric stress in the post-peak stage.

[0041] When the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress, formulas (3) and (4) are both valid; otherwise, the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress.

[0042]

[0043] ξ≥1,σ p <σ1-σ3<σ r (4)

[0044] Where, σ r σ is the residual stress, dξ is the increment of ξ caused by the change in deviatoric stress, and σ is the residual stress. p σ is the peak stress, and q is the deviatoric stress, which is the difference between the maximum principal stress σ1 and the minimum principal stress σ3.

[0045] (III) Beneficial Effects

[0046] The method of this invention solves the problem of quantitatively classifying two failure modes under true three-dimensional stress state: the normal of the failure surface is perpendicular to the direction of the intermediate principal stress, and the normal of the failure surface is perpendicular to the direction of the minimum principal stress. This provides important guidance for determining the location of surrounding rock fracture in practical engineering.

[0047] Specifically, using the stress-strain curve information obtained from rock compression-shear tests under true three-dimensional stress conditions, a quantitative classification method is provided for two typical anisotropic compression-shear failure modes of rocks under true three-dimensional stress conditions (failure where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress and failure where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress).

[0048] Furthermore, the failure mode classification method based on pre-peak deformation can predict rock failure modes, while the failure mode classification method based on post-peak deformation provides an important foundation for constructing a theory of post-peak mechanical behavior of rocks under true three-dimensional stress and a numerical simulation method for post-peak behavior of rocks. Both methods provide a basis for the accurate identification of fracture locations and effective prevention and control of fractures in the surrounding rock of deep underground engineering. Attached Figure Description

[0049] Figure 1 A flowchart illustrating a method for quantitative identification of anisotropic compression-shear failure of rocks under true three-dimensional stress, provided in an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram showing the full stress-strain curve, failure mode, and variation of ξ with deviatoric stress during the compression-shear test of gneiss under true triaxial stress state obtained at 25℃.

[0051] Figure 3This is a schematic diagram showing the full stress-strain curve, failure mode, and variation of ξ with deviatoric stress during the compression-shear test of gneiss under true triaxial stress state obtained at 100℃ real-time high temperature.

[0052] Figure 4 This is a schematic diagram showing the full stress-strain curve, failure mode, and variation of ξ with deviatoric stress during the compression-shear test of gneiss under true triaxial stress state obtained at real-time high temperature of 200℃. Detailed Implementation

[0053] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] Example 1

[0055] This invention provides a method for quantitatively identifying anisotropic compressive-shear failure of rocks under true three-dimensional stress. The method includes the following steps:

[0056] S10. Obtain a test specimen for rock compression-shear testing and conduct a rock compression-shear test on the test specimen.

[0057] For example, prepare true three-dimensional rock compression-shear test specimens and conduct rock compression-shear tests under true three-dimensional stress states.

[0058] The test specimen in this embodiment can be a cube, with the same length L and width W, and the ratio of height H to length is 2:1.

[0059] For example, L = W = 25 mm, H = 50 mm and L = W = 50 mm, H = 100 mm.

[0060] S20. Based on rock compression-shear tests, the full stress-strain relationship curve of rock compression-shear under true three-dimensional stress state was obtained;

[0061] S30. Analyze the full stress-strain relationship curve of the rock under compression and shear to obtain the characteristic strength parameters of rock under true three-dimensional stress and the anisotropic compression and shear failure mode of rock under true three-dimensional stress.

[0062] The method described in this embodiment can be used not only to identify anisotropic compressive-shear failure of rocks under normal temperature and true triaxial stress, but also to identify anisotropic compressive-shear failure of rocks under high temperature and true triaxial stress. In practical applications, it is not limited to the specific shape of the sample; the above method can be used to identify anisotropic compressive-shear failure of rocks under true three-dimensional stress.

[0063] Understandably, step S30 may include:

[0064] S31. Analyze the full stress-strain relationship curve of rock under true three-dimensional stress state;

[0065] S32. Obtain the characteristic strength parameters of rock compression and shear under true three-dimensional stress state;

[0066] S33. Divide the development stages of rock compression-shear deformation under true three-dimensional stress state;

[0067] It is understandable that the rock compression-shear deformation development stages under the true three-dimensional stress stress state include: the pre-peak deformation stage and the post-peak deformation stage;

[0068] The pre-peak deformation stage includes: linear elastic deformation stage and crack unstable propagation stage;

[0069] The post-peak deformation stage includes: stress drop stage and residual stage.

[0070] S34. Determine the deformation ratio changes in the direction of the intermediate principal stress and the direction of the minor principal stress throughout the entire process of deviatoric stress loading; wherein, the true three-dimensional stress state is σ1>σ2>σ3, where σ1 is the maximum principal stress, σ2 is the intermediate principal stress, and σ3 is the minimum principal stress;

[0071] The deformation ratio between the intermediate principal stress direction and the minor principal stress direction throughout the entire process of deviatoric stress loading is:

[0072]

[0073] Where ξ is the deformation ratio between the intermediate principal stress direction and the minor principal stress direction. D2 and D3 are the deformations measured in the intermediate principal stress direction and the minor principal stress direction, respectively, under the same deviatoric stress level. ξ is a function of deviatoric stress.

[0074] S35. Quantitatively distinguish the anisotropic compression-shear failure modes of rocks under true three-dimensional stress state.

[0075] In practical applications, rock compression-shear tests under true three-dimensional stress states cover rock compression-shear tests where the stress state conforms to σ1>σ2>σ3;

[0076] The rock compression-shear full stress-strain relationship curve is: the curve of the strain relationship between the deviatoric stress and the three principal stress directions obtained throughout the entire process from the start of loading to the failure of the specimen or the appearance of residual strength;

[0077] The characteristic strength parameters of rock compression and shear under true three-dimensional stress state include: crack initiation stress, damage stress, peak stress, and residual stress.

[0078] The method in this embodiment solves the problem of quantitatively classifying two failure modes under true three-dimensional stress state: the normal of the failure surface is perpendicular to the direction of the intermediate principal stress, and the normal of the failure surface is perpendicular to the direction of the minimum principal stress. This provides important guidance for determining the location of surrounding rock fracture in actual engineering.

[0079] Specifically, using the stress-strain curve information obtained from rock compression-shear tests under true three-dimensional stress conditions, a quantitative classification method is provided for two typical anisotropic compression-shear failure modes of rocks under true three-dimensional stress conditions (failure where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress and failure where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress).

[0080] In one possible implementation, in step S30 above, the anisotropic compression-shear failure mode of rock under true three-dimensional stress state refers to: failure where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress, and failure where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress.

[0081] One approach is to identify the failure mode of rocks under true three-dimensional stress by observing the change of ξ with deviatoric stress during the pre-peak stage.

[0082] When the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress, formulas (1) and (2) are both valid; otherwise, the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress.

[0083]

[0084] ξ≥1,σ cd <σ1-σ3<σ p (2)

[0085] Where dξ is the increment of ξ caused by the change in deviatoric stress, σ ci σ cd σ p These are the initiation stress, damage stress, and peak stress, respectively, and q is the deviatoric stress, which is the difference between the maximum principal stress σ1 and the minimum principal stress σ3.

[0086] Another method is to quantitatively identify the anisotropic compressive-shear failure mode of rock under true three-dimensional stress state by measuring the change of ξ with deviatoric stress in the post-peak stage.

[0087] When the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress, formulas (3) and (4) are both valid; otherwise, the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress.

[0088]

[0089] ξ≥1,σ p <σ1-σ3<σ r (4)

[0090] Where, σ r σ is the residual stress, dξ is the increment of ξ caused by the change in deviatoric stress, and σ is the residual stress. pσ is the peak stress, and q is the deviatoric stress, which is the difference between the maximum principal stress σ1 and the minimum principal stress σ3.

[0091] Example 2

[0092] See Figure 1 The present invention provides a flowchart illustrating a method for quantitatively identifying anisotropic compression-shear failure modes in rocks, comprising the following steps:

[0093] A1: Preparation of rock specimens for true three-dimensional compression-shear test;

[0094] A2: Conduct rock compression-shear tests under true three-dimensional stress conditions;

[0095] A3: Obtain the full stress-strain relationship curve of rock under true three-dimensional stress state;

[0096] A4: Determine the characteristic strength parameters of rock compression and shear under true three-dimensional stress state;

[0097] A5: Divide the development stages of rock compression-shear deformation under true three-dimensional stress state;

[0098] A6: Determine the changes in the deformation ratio along the intermediate principal stress direction and the minor principal stress direction throughout the entire process of deviatoric stress loading;

[0099] A7: Quantitatively distinguishes the anisotropic compression-shear failure modes of rocks under true three-dimensional stress conditions.

[0100] In step A1, the preparation of the true three-dimensional compression-shear test specimen for rock specifically involves fabricating a specimen with the same length L and width W, and a height H in a 2:1 ratio to length. The specimen is a complete rock, including isotropic and anisotropic rocks. Two representative dimensions are L = W = 25 mm, H = 50 mm and L = W = 50 mm, H = 100 mm. In this embodiment, a standard gneiss specimen with L = W = 25 mm and H = 50 mm is prepared. The gneiss in this embodiment contains bedding planes and is anisotropic.

[0101] In step A2, the rock compression-shear test under true three-dimensional stress state specifically involves conducting the rock compression-shear test under true three-dimensional stress state using rock mechanics testing equipment capable of providing the true three-dimensional stress state and corresponding initial test conditions. In this embodiment, a true triaxial shear test equipment with real-time high temperature is used to conduct the compression-shear test of gneiss under true triaxial stress state. Before the experiment, the intermediate principal stress σ2 and the minimum principal stress σ3 are set as needed. In this embodiment, based on the in-situ geostress survey results of a deep-buried tunnel, σ2 is set to 20 MPa and σ3 is set to 30 MPa. In terms of test control, force control, deformation control, and combined control methods can be selected. The loading rate can be determined based on existing literature or pre-experiments. In this embodiment, combined control is selected, specifically: when the deviatoric stress is less than the damage stress, force control is used with a loading rate of 0.5 MPa / s for the maximum principal stress; after the deviatoric stress exceeds the yield stress, deformation control is switched to the direction of the minimum principal stress with a deformation rate of 0.006 mm / min. For anisotropic rocks, such as the gneiss in this embodiment, the angles between the directions of the major principal stress and intermediate principal stress and the bedding planes of the rock can also be set. The angles between the directions of the major principal stress and intermediate principal stress and the bedding planes of the rock in this embodiment are shown in the attached figure. Figure 2 Appendix Figure 3 Appendix Figure 4 As shown. Where β is the angle between the major principal stress direction and the bedding plane, and ω is the angle between the intermediate principal stress direction and the bedding plane. In this embodiment, the principal stress direction is determined by the angle between the surrounding rock structural plane of a deep-buried tunnel and the geostress direction. Specific experimental methods for rock compression-shear tests under true triaxial stress at room temperature can be found in publicly published literature in this field. For rock compression-shear tests under true triaxial stress with real-time high temperature, an additional heat preservation process is required, specifically: heat preservation for 2 hours before biaxial stress loading.

[0102] In step A3, the stress-strain relationship curves of rock under true three-dimensional stress state are obtained, specifically the strain-strain relationship curves in the direction of the major principal stress, the strain-strain relationship curves in the direction of the intermediate principal stress, and the strain-strain relationship curves in the direction of the minimum principal stress. See the results below. Figure 2 , Figure 3 , Figure 4 .

[0103] In step A4, the characteristic strength parameters of rock under true three-dimensional stress state are determined, specifically: crack initiation stress, yield stress, peak stress, and residual stress. The method for determining these characteristic strength parameters is as follows:

[0104] The initiation stress can be determined using the lateral strain method in rock mechanics.

[0105] The yield stress is the deviatoric stress corresponding to the maximum volumetric strain on the curve relating deviatoric stress and volumetric strain.

[0106] Peak stress is the maximum value of the deviatoric stress on the curve relating strain and deviatoric stress in the direction of maximum principal stress.

[0107] The residual stress is the deviatoric stress value when the deviatoric stress is stable on the curve of strain and deviatoric stress in the direction of maximum principal stress after the peak stage.

[0108] Depend on Figure 2 , Figure 3 , Figure 4 The stress-strain curves shown determine the initiation stress, yield stress, peak stress, and residual stress of gneiss under true triaxial stress at real-time temperatures of 25℃, 100℃, and 200℃, respectively.

[0109] The initiation stresses at 25℃, 100℃, and 200℃ were 117.3 MPa, 168.7 MPa, and 108.9 MPa, respectively.

[0110] The yield stresses at 25℃, 100℃, and 200℃ are 186.7MPa, 263.7MPa, and 170.9MPa, respectively.

[0111] The peak stresses at 25℃, 100℃, and 200℃ are 245.9MPa, 330.6MPa, and 208.9MPa, respectively.

[0112] The initiation stresses at 25℃, 100℃, and 200℃ were 87.4MPa, 121.9MPa, and 112.8MPa, respectively.

[0113] In step A5, the development stages of rock compression-shear deformation under true three-dimensional stress are divided, mainly including the pre-peak deformation stage and the post-peak deformation stage. The pre-peak deformation stage specifically includes: the linear elastic deformation stage and the crack instability propagation stage. The post-peak deformation stage specifically includes: the stress drop stage and the residual stage. The specific methods for determining each deformation stage are as follows:

[0114] When the deviatoric stress is between the crack initiation stress and the damage stress, the rock is in the linear elastic deformation stage;

[0115] When the deviatoric stress is between the damage stress and the peak stress, the rock is in the unstable crack propagation stage.

[0116] When the deviatoric stress is between the peak stress and the residual stress, the rock is in the stress drop stage;

[0117] After residual stress occurs, the rock is in the residual stage.

[0118] See Figure 2 , Figure 3 , Figure 4Based on the initiation stress, yield stress, peak stress, and residual stress determined in step A4, the deformation stages of gneiss under true triaxial stress states obtained at real-time high temperatures of 25℃, 100℃, and 200℃ are divided. Figure 2 , Figure 3 , Figure 4 In the diagram, I, II, III, and IV represent the linear elastic deformation stage, the crack instability propagation stage, the stress drop stage, and the residual stage, respectively.

[0119] In step A6, the changes in the deformation ratios along the intermediate principal stress direction and the minor principal stress direction throughout the entire deviatoric stress loading process are determined. Specifically, the deformation ratios along the intermediate principal stress direction and the minor principal stress direction are as follows:

[0120]

[0121] Where ξ is the deformation ratio in the direction of the intermediate principal stress and the direction of the minor principal stress. D2 and D3 are the deformations in the directions of the intermediate principal stress and the minor principal stress, respectively, measured under the same deviatoric stress level.

[0122] Figure 2 , Figure 3 , Figure 4 The evolution of ξ with deviatoric stress in the compression-shear test of gneiss under true triaxial stress at temperatures of 25℃, 100℃, and 200℃ is presented.

[0123] In step A7, the anisotropic compressive-shear failure modes of rock under true three-dimensional stress state are quantitatively distinguished. (See also...) Figure 2 , Figure 3 , Figure 4 Under true three-dimensional stress, rocks exhibit two main failure modes: failure where the normal to the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress, and failure where the normal to the macroscopic fracture surface is perpendicular to the direction of the minor principal stress. These failure modes can be quantitatively distinguished using two methods provided in this invention, specifically:

[0124] The first method identifies the failure mode of rocks under true three-dimensional stress conditions by examining the variation of ξ with deviatoric stress during the pre-peak stage. See also Figure 4 When failure occurs where the normal to the macroscopic fracture surface is perpendicular to the direction of the minor principal stress, the following two formulas hold simultaneously; otherwise, failure occurs when the normal to the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress (see appendix). Figure 2 Appendix Figure 3 ).

[0125]

[0126] ξ≥1,σ cd <σ1-σ3<σ p

[0127] Where dξ is the increment of ξ caused by the change in deviatoric stress, σci σ cd σ p These are the initiation stress, damage stress, and peak stress, respectively, and q is the deviatoric stress, which is the difference between the maximum principal stress σ1 and the minimum principal stress σ3.

[0128] The second method is to quantitatively identify the anisotropic compressive-shear failure mode of rock under true three-dimensional stress state by observing the change of ξ with deviatoric stress in the post-peak stage. See also Figure 4 When failure occurs where the normal to the macroscopic fracture surface is perpendicular to the direction of the minor principal stress, the following two formulas hold simultaneously. Otherwise, failure occurs when the normal to the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress. Figure 2 , Figure 3 ).

[0129]

[0130] ξ≥1,σ p <σ1-σ3<σ r

[0131] Where, σ r This represents residual stress.

[0132] In this embodiment, using the stress-strain curve information obtained from rock compression-shear tests under true three-dimensional stress conditions, a quantitative classification method is provided for two typical anisotropic compression-shear failure modes of rocks under true three-dimensional stress conditions (failure where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress and failure where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress).

[0133] The failure mode classification method based on pre-peak deformation can predict rock failure modes, while the failure mode classification method based on post-peak deformation provides an important foundation for constructing a theory of post-peak mechanical behavior of rocks under true three-dimensional stress and a numerical simulation method for post-peak behavior of rocks. Both methods provide a basis for the accurate identification of fracture locations and effective prevention and control of fractures in the surrounding rock of deep underground engineering.

[0134] It should be noted that any reference numerals placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In claims that enumerate several means, several of these means may be embodied by the same hardware. The use of the terms first, second, third, etc., is merely for convenience of expression and does not indicate any order. These terms can be understood as part of the component names.

[0135] Furthermore, it should be noted that in the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0136] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the claims should be interpreted to include both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0137] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, then this invention should also include these modifications and variations.

Claims

1. A method for quantitative identification of anisotropic compressive-shear failure of rocks under true three-dimensional stress, characterized in that, include: S10. Obtain a test specimen for rock compression-shear testing and conduct a rock compression-shear test on the test specimen. S20. Based on rock compression-shear tests, the full stress-strain relationship curve of rock compression-shear under true three-dimensional stress state was obtained; S30. Analyze the full stress-strain relationship curve of the rock under compression and shear to obtain the characteristic strength parameters of rock under true three-dimensional stress and the anisotropic compression and shear failure mode of rock under true three-dimensional stress. S30 includes: S31. Analyze the full stress-strain relationship curve of rock under true three-dimensional stress state; S32. Obtain the characteristic strength parameters of rock compression and shear under true three-dimensional stress state; S33. Divide the development stages of rock compression-shear deformation under true three-dimensional stress state; S34. Determine the deformation ratio changes along the intermediate principal stress direction and minor principal stress direction throughout the entire process of deviatoric stress loading; wherein, the true three-dimensional stress state is... , For the maximum principal stress, The intermediate principal stress, It is the minimum principal stress; S35. Quantitatively distinguish the anisotropic compression-shear failure modes of rocks under true three-dimensional stress conditions; S34 includes: The deformation ratio between the intermediate principal stress direction and the minor principal stress direction throughout the entire process of deviatoric stress loading is: ； in, The deformation ratio along the intermediate principal stress direction and the minor principal stress direction and These are the deformations measured in the directions of the intermediate principal stress and minor principal stress, respectively, under the same level of deviatoric stress. It is a function of deviatoric stress; The anisotropic compression-shear failure mode of rock under true three-dimensional stress state refers to: failure in which the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress, and failure in which the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress. The S35 includes: Through the pre-peak phase Identify the failure modes of rocks under true three-dimensional stress conditions by varying the deviatoric stress. When the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress, formulas (1) and (2) are valid simultaneously; otherwise, the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress. （1）； （2）； in, Caused by changes in eccentric stress The increment, , , These are the initiation stress, damage stress, and peak stress, respectively. This is the deviatoric stress, and its value is the maximum principal stress. and minimum principal stress The difference; The S35 includes: Through the post-peak phase Quantitatively identify the anisotropic compressive-shear failure mode of rock under true three-dimensional stress state by varying the deviatoric stress. When the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the minor principal stress, formulas (3) and (4) are simultaneously valid; otherwise, the failure occurs where the normal of the macroscopic fracture surface is perpendicular to the direction of the intermediate principal stress. （3）； （4）； in, For residual stress, Caused by changes in eccentric stress The increment, Peak stress, This is the deviatoric stress, and its value is the maximum principal stress. and minimum principal stress The difference.

2. The method for quantitative identification of anisotropic compression-shear failure of rocks under true three-dimensional stress according to claim 1, characterized in that, S10 includes: Prepare true three-dimensional rock compression-shear test specimens and conduct true three-dimensional rock compression-shear tests under stress conditions; The test specimen is a cube with the same length L and width W, and the ratio of height H to length is 2:

1.

3. The method for quantitative identification of anisotropic compression-shear failure of rocks under true three-dimensional stress according to claim 1, characterized in that, The true three-dimensional stress state rock compression-shear test covers stress states that conform to Rock compression-shear test; The rock compression-shear full stress-strain relationship curve is: the curve of the strain relationship between the deviatoric stress and the three principal stress directions obtained throughout the entire process from the start of loading to the failure of the specimen or the appearance of residual strength; The characteristic strength parameters of rock compression and shear under true three-dimensional stress state include: crack initiation stress, damage stress, peak stress, and residual stress.

4. The method for quantitative identification of anisotropic compression-shear failure of rocks under true three-dimensional stress according to claim 1, characterized in that, The rock compression-shear deformation development stages under true three-dimensional stress stress state include: pre-peak deformation stage and post-peak deformation stage; The pre-peak deformation stage includes: linear elastic deformation stage and crack unstable propagation stage; The post-peak deformation stage includes: stress drop stage and residual stage.

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