Deep rock mass stress state characterization method based on rock strength nondimensionalization

Abstract

The invention provides a deep rock mass stress state characterization method based on rock strength nondimensionalization, and belongs to the field of rock mechanics engineering. The method comprises the following steps: firstly, acquiring true three-dimensional stress of a rock mass and basic mechanical parameters of the rock, then carrying out dimensionless processing on principal stress according to the ratio of stress to rock strength parameters, and constructing a stress difference coefficient based on dimensionless stress difference to represent the three-dimensional stress non-uniformity. According to the method, the absolute magnitude of stress, the strength closeness and the three-dimensional stress non-uniformity can be reflected at the same time, and a universal and scientific evaluation system is provided for deep rock mass health evaluation, dynamic disaster prediction and underground engineering design.

Description

Technical Field

[0001] This invention relates to the technical field of rock mechanics engineering, and more particularly to a method for characterizing the stress state of deep rock masses based on dimensionless rock strength. Background Technology

[0002] As mining and underground space development rapidly advance into deeper areas, rock masses in deep engineering are generally in high triaxial stress environments. Traditional methods for describing stress states typically use the maximum principal stress. Intermediate principal stress and minimum principal stress The absolute value of the principal stress is used to characterize the rock mass. While this method is intuitive in form, it has significant limitations under deep, high-stress conditions. First, the magnitude of the absolute stress value only reflects the magnitude of the stress itself and cannot reflect the relationship between the stress level and the rock strength. Under different lithological conditions, even with the same absolute stress value, the corresponding failure risk and stability state may be completely different, making it difficult to accurately assess the stability or near-failure level of the rock mass by relying solely on the absolute value of the principal stress.

[0003] Therefore, a new method is needed that can simultaneously reflect the magnitude of absolute stress, the degree of similarity in relative rock strength, and the differences in triaxial stress, so as to simply and clearly reflect the degree of rock failure and significantly improve the scientificity and applicability of stress characterization, in order to meet the evaluation needs of high-stress conditions in deep engineering. Summary of the Invention

[0004] In response to the technical problems mentioned in the background section, this invention provides a method for characterizing the stress state of deep rock masses based on dimensionless rock strength. When describing the stress state at any point within a rock mass, the stress parameters obtained by this method have the following advantages: they enable unified quantification and comparability of stress states under different lithological conditions; they not only reflect the absolute magnitude of the force on the rock mass but also accurately reflect the degree of proximity of the stress level at that point to the rock's failure strength, thus reflecting the asymptotic characteristics of failure risk; they can quantitatively characterize the triaxial stress inhomogeneity commonly found in deep engineering; and they can reflect the strength control effect in the rock constitutive relationship, providing more physically meaningful stress indicators for revealing the intrinsic mechanism of the mechanical response of deep rock masses.

[0005] The technical means employed in this invention are as follows: A method for characterizing the stress state of deep rock masses based on dimensionless rock strength includes the following steps: S1. Obtain the triaxial in-rock stress and basic mechanical parameters of the target rock mass; S2. Based on the ratio of stress to the corresponding rock strength parameter, the principal stresses are dimensionless to construct the principal stress intensity ratio, and the stress difference coefficient is calculated according to the principal stress intensity ratio. S3. Restate the generalized Hooke's law within the dimensionless stress framework so that it can reflect the degree of approximation of the stress level to the rock strength, thereby achieving a comprehensive characterization of the stress state of deep rock masses.

[0006] Furthermore, obtaining the basic mechanical parameters and stress state of the rock includes: taking samples on site according to specifications, processing and manufacturing standard rock specimens according to relevant test specifications, and conducting uniaxial compressive strength tests, Brazilian splitting tests, and direct shear tests to obtain the rock's strength parameters.

[0007] Furthermore, the ratio of the stress to the corresponding rock strength parameter characterizes the stress in each direction, and the stress difference coefficient is calculated; The magnitude of the stress on the rock and the uniaxial compressive strength of the rock are used. Both stress levels and the degree of stress variability are commonly characterized; among them, the stress state is represented by the maximum principal stress. The intermediate principal stress is and the minimum principal stress is .

[0008] Furthermore, the step of characterizing each principal stress based on the ratio of stress to the corresponding rock strength parameter and calculating the stress difference coefficient includes: using the magnitude of the principal stress at a certain measuring point in the rock mass and the uniaxial compressive strength of the rock. The ratio simultaneously characterizes the stress level and the degree of stress difference at the measuring point.

[0009] Furthermore, the stress difference coefficient is based on the ratio of the dimensionless principal stress difference to the maximum principal stress.

[0010] Furthermore, the value of the stress difference coefficient is normalized to within the range of 0 to 1.

[0011] Furthermore, the restatement of the generalized Hooke's law uses dimensionless principal stress as the input variable.

[0012] Furthermore, the dimensionless principal stress intensity ratio is used to construct a rock mass health index.

[0013] Furthermore, the health index is used for rockburst risk prediction and tunnel support optimization design.

[0014] Compared with the prior art, the present invention has the following advantages: This invention eliminates the incomparability of stresses across different lithologies and depths, and adopts a dimensionless standard to unify stress description. This invention can quantitatively reflect the degree of rock failure proximity, and can be used for health assessment and risk warning. This invention appears to be more applicable to deep stress-uniform environments, and the proposed difference coefficient has greater engineering significance.

[0015] Therefore, the method of the present invention can be used for rockburst prediction, support optimization, stability assessment, etc., which significantly improves the scientificity and applicability of stress characterization. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is the overall flowchart of the present invention.

[0018] Figure 2(a) is a schematic diagram of the stress state.

[0019] Figure 2(b) shows the original method description of the circumferential stress field: the maximum value is 62.97 MPa.

[0020] Figure 2(c) shows the description of the new method for circumferential stress field: the maximum value for granite is 0.28.

[0021] Figure 2(d) shows the description of the new method for circumferential stress field: the maximum value for sandstone is 0.94. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] like Figure 1As shown, this invention provides a method for characterizing the stress state of deep rock masses based on dimensionless rock strength, comprising the following steps: S1. Obtain the triaxial protolith stress and basic mechanical parameters of the target rock mass; S1 includes the following steps for obtaining the triaxial protolith stress and basic mechanical parameters of the target rock mass: S11: Based on the requirements of the on-site investigation, stress test points are set up in the target area, and the maximum principal stress, intermediate principal stress and minimum principal stress are determined by water pressure fracturing method, acoustic emission stress inversion method or other in-situ testing methods. S12: Take rock samples near the test point according to the specifications, and perform visual inspection, numbering and preservation of the rock cores; S13: The sampled rock cores are processed into standard rock specimens according to relevant testing standards, and uniaxial compressive strength test, Brazilian splitting test and shear test are carried out to obtain mechanical parameters such as uniaxial compressive strength, tensile strength, cohesion and internal friction angle of the rock.

[0025] S2. Based on the ratio of stress to the corresponding rock strength parameter, the principal stresses are dimensionless to construct the principal stress intensity ratio, and the stress difference coefficient is calculated according to the principal stress intensity ratio. In S2, based on the ratio of stress to the corresponding rock strength parameter, each principal stress is dimensionlessly processed to construct the principal stress intensity ratio, and the stress difference coefficient is calculated according to the principal stress intensity ratio, including the following steps: S21: Select rock strength parameters that represent the strength characteristics of the rock mass material, including uniaxial compressive strength. ,tensile strength wait.

[0026] S22: The maximum principal stresses are respectively... Intermediate principal stress and minimum principal stress Dividing by the strength parameter, the principal stress components described by the stress-intensity ratio are respectively , and : , , ; but, , , ; That is, the stress state at a certain point in the rock mass can be used as... , , as well as In this way, its advantage is that it can reflect both the absoluteness of the stress level and the relative level of the stress level and the relative strength of the rock.

[0027] S23: Based on the dimensionless principal stress intensity ratio, stress difference coefficients λ12 and λ13 are constructed to characterize triaxial stress inhomogeneity. These stress difference coefficients are calculated using the following formula: ; ; but, , ; in, and The larger the value, the greater the degree of anisotropic stress difference at that point.

[0028] S24: The stress difference coefficient is limited to a range of 0 to 1 to facilitate unified comparison and engineering application under different rock mass conditions. The larger the value, the greater the stress difference.

[0029] S3. Restate the generalized Hooke's law within the dimensionless stress framework so that it can reflect the degree of approximation of the stress level to the rock strength, thereby achieving a comprehensive characterization of the stress state of deep rock masses.

[0030] Example 1 As an embodiment of the present invention, the method in this embodiment provides a method for characterizing the stress state of deep rock masses based on dimensionless rock strength, including the following steps: S1: Taking a deep tunnel project as an example, the tunnel traverses different strata along its construction route, encountering two types of surrounding rock with significantly different lithologies. The first section of surrounding rock is mainly composed of relatively dense granodiorite, with high strength and intact structure; the second section is composed of gneissic schist, with well-developed joints and significantly lower mechanical strength. When excavating to the lithology transition zone, the measured stress levels of the original rock are basically similar, but due to the significant difference in strength parameters between the two types of rock masses, the stability of the two sections of surrounding rock under the same stress is drastically different. The horizontal stress measured at the same measuring point on site is... Vertical stress .

[0031] S2: On-site sampling and preparation of standard specimens, and uniaxial compressive strength, Brazilian splitting, and direct shear tests according to specifications to obtain uniaxial compressive strength, tensile strength, cohesion and internal friction angle, and elastic modulus. Compared with Poisson Indoor mechanical parameter test results show that the uniaxial compressive strength of lithology A granite is... elastic modulus Poisson's ratio Compressive strength of sandstone of lithology B elastic modulus Poisson's ratio .

[0032] S3: The stress state of rocks is characterized by dimensionless strength ratio. Lithology A (Granite): ; ; Lithology B (sandstone): ; ; Intuitive meaning: Under the same engineering conditions and geostress, low-strength rock (B) is closer to the failure threshold.

[0033] S4: The stress difference coefficient is used to characterize the degree of stress difference in rocks. ; ; S5: The circumferential stress solution near the tunnel under this stress state, obtained through numerical simulation, is shown in Figure 2(b). The circumferential stress fields of tunnels with different lithologies are obtained using the dimensionless stress-intensity ratio proposed in this invention, as shown in Figures 2(c) and 2(d). It is evident that under the same stress state, the surrounding rock of the granite tunnel is at a lower stress level, with a stress-intensity ratio of only 0.28, indicating higher safety. In contrast, the maximum stress around the sandstone tunnel is close to its compressive strength, with a stress-intensity ratio reaching 0.94, indicating an extremely high stress level and a very high risk of local failure. Therefore, under the same deep geostress level, the surrounding rock of tunnels in rock masses with lower strength is in a high stress state and has a high risk of failure. The method disclosed in this invention effectively demonstrates these characteristics. Thus, this method presents a greater amount of information and is more scientifically sound.

[0034] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. In the above embodiments of the present invention, the descriptions of each embodiment have their own emphasis; parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments. It should be understood that the disclosed technical content in the several embodiments provided in this application can be implemented in other ways.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for characterizing the stress state of deep rock masses based on dimensionless rock strength, characterized in that, Includes the following steps: S1. Obtain the triaxial in-rock stress and basic mechanical parameters of the target rock mass; S2. Based on the ratio of stress to the corresponding rock strength parameter, the principal stresses are dimensionless to construct the principal stress intensity ratio, and the stress difference coefficient is calculated according to the principal stress intensity ratio. S3. Restate the generalized Hooke's law within the dimensionless stress framework so that it can reflect the degree of approximation of the stress level to the rock strength, thereby achieving a comprehensive characterization of the stress state of deep rock masses.

2. The method for characterizing the stress state of deep rock masses based on dimensionless rock strength according to claim 1, characterized in that, The process of obtaining the basic mechanical parameters and stress state of the rock includes: taking samples on site according to specifications, processing and manufacturing standard rock specimens according to relevant test specifications, and conducting uniaxial compressive strength tests, Brazilian splitting tests and direct shear tests to obtain the rock strength parameters.

3. The method for characterizing the stress state of deep rock masses based on dimensionless rock strength according to claim 1, characterized in that, The ratio of stress to the corresponding rock strength parameter characterizes the stress in each direction and calculates the stress difference coefficient. The magnitude of the stress on the rock and the uniaxial compressive strength of the rock are used. Both characterize the stress level and the degree of stress difference; Among them, the stress state is represented by the maximum principal stress. The intermediate principal stress is and the minimum principal stress is .

4. The method for characterizing the stress state of deep rock masses based on dimensionless rock strength according to claim 1, characterized in that, The steps of characterizing each principal stress based on the ratio of stress to the corresponding rock strength parameter and calculating the stress difference coefficient include: using the magnitude of the principal stress at a certain measuring point in the rock mass and the uniaxial compressive strength of the rock. The ratio simultaneously characterizes the stress level and the degree of stress difference at the measuring point.

5. The method for characterizing the stress state of deep rock masses based on dimensionless rock strength according to claim 1, characterized in that, The stress difference coefficient is based on the ratio of the dimensionless principal stress difference to the maximum principal stress.

6. The method for characterizing the stress state of deep rock masses based on dimensionless rock strength according to claim 1, characterized in that, The value of the stress difference coefficient is normalized to within 0 to 1.

7. The method for characterizing the stress state of deep rock masses based on dimensionless rock strength according to claim 1, characterized in that, The restatement of the generalized Hooke's law uses dimensionless principal stress as the input variable.

8. The method for characterizing the stress state of deep rock masses based on dimensionless rock strength according to claim 1, characterized in that, The dimensionless principal stress intensity ratio is used to construct the rock mass health index.

9. A method for characterizing the stress state of deep rock masses based on dimensionless rock strength according to claim 8, characterized in that, The health index is used for rockburst risk prediction and tunnel support optimization design.

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