Layered rock mass transverse isotropic damage calculation method

Abstract

The invention discloses a method for calculating transverse isotropic damage of layered rock mass, and aims to overcome the defect of deterioration of mechanical properties of limestone in an acid environment in the prior art. According to the method, a chemical damage variable and a mechanical damage variable are integrated, a total damage variable is obtained through coupling, and the elastic modulus and compressive strength of the rock mass are corrected accordingly. The method comprises the following specific steps: acquiring a pH value and a bedding dip angle of a limestone sample environment, monitoring an accumulated ringing count in a loading process, and acquiring a crack density and a void ratio of a limestone mass sample by using a scanning electron microscope; calculating a chemical damage variable and a mechanical damage variable; coupling to obtain a total damage variable; and correcting the elastic modulus and compressive strength of the rock mass based on the total damage variable, the initial elastic modulus and the initial shear modulus obtained through coupling. The method can accurately reflect the influence of acidic underground water on the mechanical properties of limestone, improves the real-time performance and accuracy of evaluation, and is suitable for rock mass damage evaluation in a complex geological environment.

Description

Technical Field

[0001] The invention relates to a method for calculating transversely isotropic damage of a layered rock mass, and belongs to the technical field of limestone damage assessment. Background Art

[0002] In the process of tunnel excavation, underground mine development and other underground engineering construction, rock mass stability assessment is a key link to ensure engineering safety and economic benefits. The mechanical properties of rock mass directly affect the construction difficulty, cost and long-term stability of the project, especially in areas with acidic groundwater. The corrosive effect of acidic water on rock will significantly weaken the mechanical properties of rock mass and increase the risk of engineering disasters.

[0003] Traditional rock mass stability assessment methods mainly rely on laboratory physical and mechanical tests and empirical formulas, which can reflect the mechanical properties of rocks to a certain extent. However, with the increasing complexity of engineering geological conditions, especially in the presence of acidic environments, traditional methods have significant limitations in accurately predicting the deterioration of rock mass mechanical properties.

[0004] In recent years, researchers have begun to explore the combination of continuous damage theory, Weibull distribution theory and rock micro-element strength theory in the modeling of rock damage and failure. The continuous damage theory describes the cumulative effect of microcracks and defects in the rock by introducing damage variables, while the Weibull distribution theory is used to describe the statistical distribution characteristics of rock micro-element strength. The rock micro-element strength theory regards rock as a collection of many micro-elements, each of which has independent strength characteristics. The combination of these theories has improved the accuracy of rock damage and failure models to a certain extent.

[0005] However, existing models often ignore the anisotropic properties of rocks when dealing with layered rock masses (such as limestone with different bedding angles), and cannot fully reflect the coupling effect of chemical damage and mechanical damage in acidic environments. In addition, many existing models fail to effectively combine dynamic monitoring data in actual projects, making it difficult to achieve real-time evaluation and early warning, limiting their application in actual projects.

[0006] In an acidic environment, acidic substances in groundwater (such as sulfuric acid and nitric acid) react chemically with carbonate minerals in rocks, resulting in changes in the pore structure of rocks and weakening of the bonding force between mineral particles, thereby causing the deterioration of the mechanical properties of rocks. This chemical damage interacts with the mechanical damage caused by external loads, making the overall mechanical behavior of the rock mass more complex and difficult to predict. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for calculating transversely isotropic damage of layered rock mass to overcome the shortcomings of the prior art.

[0008] The technical solution of the present invention is: a method for calculating transversely isotropic damage of layered rock mass, the method comprising the following steps:

[0009] a) Obtain the pH value p of the solution in the environment of the limestone rock sample, obtain the bedding inclination α of the limestone rock sample, monitor the cumulative ringing count of the limestone rock sample during loading by an acoustic emission instrument, and obtain the crack density ρ of the limestone rock sample using a scanning electron microscope c and void ratio φ;

[0010] b) Calculate the chemical damage variable D based on p and α c ;

[0011] c) Acoustic emission instrument monitors the cumulative ringing counts of rock samples during loading to calculate the mechanical damage variable D m ;

[0012] d) The chemical damage variable D calculated in step b) and step c) c and mechanical damage variable D m The total damage variable D is obtained by coupling;

[0013] e) Based on the total damage variable D and initial elastic modulus E o and the initial shear modulus G o Modify the elastic modulus E′ and compressive strength σ′ of the rock mass.

[0014] Furthermore, the chemical damage variable D c The calculation method is:

[0015]

[0016] Among them, β1, β2, β3, β4, β5, β6, β7, β8, β9 and β 10 is the fitting parameter.

[0017] Furthermore, the mechanical damage variable D m The calculation method is:

[0018]

[0019] Where a represents the scale parameter of the Weibull distribution, m represents the shape parameter of the Weibull distribution, and η1 is the fitting parameter.

[0020] Further,

[0021] Where a represents the scale parameter of the Weibull distribution, m represents the shape parameter of the Weibull distribution, γ represents the coefficient used to adjust the relationship between stress and the cumulative ringing number of acoustic emission, Nm represents the theoretical maximum ringing number that the specimen should reach when it is completely destroyed, Nd represents the cumulative number of acoustic emission events recorded by the acoustic emission monitoring system during the loading process, and f represents the current stress level during the loading process.

[0022] Furthermore, the calculation method of the total damage variable D is:

[0023] D=D c +D m -D c D m

[0025] Furthermore, the method for correcting the compressive strength of the rock mass is:

[0026] E′=E o (1-D)

[0027] Where E′ represents the corrected compressive strength of the rock mass.

[0028] Furthermore, the method for correcting the elastic modulus of the rock mass is:

[0029] G′=G o (1-D)

[0030] Where G′ represents the corrected elastic modulus of the rock mass.

[0031] Furthermore, the limestone rock mass sample in step a) is a sub-limestone rock mass sample obtained by evenly dividing the original limestone sample using a three-dimensional grid.

[0032] Furthermore, the total damage variable of the original limestone sample is calculated as follows:

[0033]

[0034] Among them, D total represents the total damage variable of the original limestone sample, D i The total damage variable of the i-th sub-limestone rock mass sample obtained by uniform segmentation of the three-dimensional grid, ω i Represents the weight of the i-th sub-limestone rock mass sample.

[0035] Furthermore, the weight of the i-th sub-limestone rock mass sample is calculated as follows:

[0036]

[0037] Among them, R i The dissolution rate of the i-th sub-limestone rock sample, Vi The volume of the i-th sub-limestone rock sample.

[0038] The beneficial effects of the present invention are: compared with the prior art,

[0039] 1) The present invention comprehensively considers the coupling effect of chemical damage and mechanical damage, especially in acidic environments, and can more accurately reflect the weakening mechanism of acidic groundwater on the mechanical properties of limestone. Secondly, by introducing environmental parameters such as bedding inclination α and pH value p, and using an acoustic emission instrument to monitor the ring count in real time, the method effectively captures the dynamic damage evolution process of the rock mass under actual engineering conditions, improving the real-time and accuracy of the assessment;

[0040] 2) The present invention uses a scanning electron microscope to obtain the crack density and porosity of the limestone rock sample, and uses the microstructure to adjust the chemical and mechanical damage variables, thereby more accurately reflecting the damage of the rock mass in a complex environment;

[0041] 3) The present invention adopts a modeling method that combines continuous damage theory, Weibull distribution theory and rock micro-element strength theory, fully considering the anisotropic characteristics of rocks, and improving the adaptability and prediction accuracy of the model to complex geological conditions;

[0042] 4) The present invention adopts the method of uniform segmentation of three-dimensional grids and weight calculation to calculate the damage variables of each region according to its chemical composition, bedding dip and other characteristics, and comprehensively evaluate the damage state of the overall rock mass. It can systematically consider the heterogeneity of rocks, accurately calculate the chemical and mechanical damage variables of each region, and comprehensively evaluate the damage state of the overall rock mass. This not only improves the comprehensiveness and accuracy of the method, but also enhances the applicability and practical value of the method in complex geological environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0044] Implementation Example 1: Reference Figure 1 ,

[0045] Experimental materials and equipment

[0046] 1. Limestone sample preparation:

[0047] ●Select natural layered limestone samples with dimensions of 50mm×50mm×100mm.

[0048] ●Use the three-dimensional grid to evenly divide the original limestone sample into 10 sub-limestone samples.

[0049] The size is 50mm×50mm×10mm.

[0050] 2. Equipment configuration:

[0051] ●Acoustic emission instrument (AE instrument): used to monitor the cumulative ring count (Nd) of the limestone sample during loading. ●Uniaxial compression testing machine: used to apply axial stress and record stress-strain curves.

[0052] ●pH meter: used to measure the pH value of the solution in which the rock sample is located.

[0053] Inclinometer: used to measure the bedding dip angle α of limestone samples.

[0054] Porosity measurement equipment (such as nuclear magnetic resonance NMR): used to determine the porosity φ of each area. Scanning electron microscope (SEM): used to observe the microscopic pore structure of rock samples.

[0055] Implementation steps

[0056] A method for calculating transversely isotropic damage of layered rock mass comprises the following steps:

[0057] a) Obtain the pH value p of the solution in the environment of the limestone rock sample, obtain the bedding inclination α of the limestone rock sample, monitor the cumulative ringing count of the limestone rock sample during loading by an acoustic emission instrument, and obtain the crack density ρ of the limestone rock sample using a scanning electron microscope c and void ratio φ;

[0058]

[0059] L T For limestone rock samples

[0060] L T is the total crack length of the limestone rock sample, A represents the observed cross-sectional area of ​​the limestone rock sample, and d

[0061] is the thickness of the limestone rock mass sample;

[0062]

[0063] π is the total pore area of ​​the limestone rock mass sample.

[0064] b) Calculate the chemical damage variable d based on p and α c ;

[0065] c) Acoustic emission instrument monitors the cumulative ringing counts of rock samples during loading to calculate the mechanical damage variable D m ;

[0066] d) The chemical damage variable d calculated in step b) and step c) c and mechanical damage variable D mThe total damage variable D is obtained by coupling;

[0067] e) Based on the total damage variable D and initial elastic modulus E o and the initial shear modulus G o Modify the elastic modulus E′ and compressive strength σ′ of the rock mass.

[0068] Furthermore, the chemical damage variable D c The calculation method is:

[0069]

[0070] Among them, β1, β2, β3, β4, β5, β6, β7, β8, β9 and β 10 are fitting parameters. β1, β2, β3, β4, β5, β6, β7, β8, β9 and β 10 .

[0071] Furthermore, the mechanical damage variable D m The calculation method is:

[0072]

[0073] Where a represents the scale parameter of the Weibull distribution, m represents the shape parameter of the Weibull distribution, and η1 is the fitting parameter, which is obtained by data fitting.

[0074] Further,

[0075] Where a represents the scale parameter of the Weibull distribution, m represents the shape parameter of the Weibull distribution, γ represents the coefficient used to adjust the relationship between stress and the cumulative ringing number of acoustic emission, Nm represents the theoretical maximum ringing number that the specimen should reach when it is completely destroyed, Nd represents the cumulative number of acoustic emission events recorded by the acoustic emission monitoring system during the loading process, and f represents the current stress level during the loading process.

[0076] Furthermore, the calculation method of the total damage variable D is:

[0077] D=D c +D m -D c D m

[0079] Furthermore, the method for correcting the compressive strength of the rock mass is:

[0080] E′=E o (1-D)

[0081] Where E′ represents the corrected compressive strength of the rock mass.

[0082] Furthermore, the method for correcting the elastic modulus of the rock mass is:

[0083] G′=G o (1-D)

[0084] Where G′ represents the corrected elastic modulus of the rock mass.

[0085] Furthermore, the limestone rock mass sample in step a) is a sub-limestone rock mass sample obtained by evenly dividing the original limestone sample using a three-dimensional grid.

[0086] Furthermore, the total damage variable of the original limestone sample is calculated as follows:

[0087]

[0088] Among them, D total represents the total damage variable of the original limestone sample, D i The total damage variable of the i-th sub-limestone rock mass sample obtained by uniform segmentation of the three-dimensional grid, ω i Represents the weight of the i-th sub-limestone rock mass sample.

[0089] Furthermore, the weight of the i-th sub-limestone rock mass sample is calculated as follows:

[0090]

[0091] Among them, R i The dissolution rate of the i-th sub-limestone rock sample, V i The volume of the i-th sub-limestone rock sample.

[0092] The parts not described in detail in the present invention are all known technologies to those skilled in the art. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for calculating transversely isotropic damage of layered rock mass, characterized in that: The method comprises the following steps: a) Obtain the pH value p of the solution in the environment of the limestone rock sample, obtain the bedding inclination α of the limestone rock sample, monitor the cumulative ringing count of the limestone rock sample during loading by an acoustic emission instrument, and obtain the crack density ρ of the limestone rock sample using a scanning electron microscope c and void ratio φ; b) Calculate the chemical damage variable D based on p and α c ; c) Acoustic emission instrument monitors the cumulative ringing counts of rock samples during loading to calculate the mechanical damage variable D m ; d) The chemical damage variable D calculated in step b) and step c) c and mechanical damage variable D m The total damage variable D is obtained by coupling; e) Based on the total damage variable D and initial elastic modulus E o and the initial shear modulus G o Modify the elastic modulus E′ and compressive strength σ′ of the rock mass.

2. The method for calculating transversely isotropic damage of layered rock mass according to claim 1, characterized in that: The chemical damage variable D c The calculation method is: Among them, β1, β2, β3, β4, β5, β6, β7, β8, β9 and β 10 to fit the parameters.

3. The method for calculating transversely isotropic damage of layered rock mass according to claim 1, characterized in that: The mechanical damage variable D m The calculation method is: Where a represents the scale parameter of the Weibull distribution, m represents the shape parameter of the Weibull distribution, and η1 is the fitting parameter.

4. The method for calculating transversely isotropic damage of layered rock mass according to claim 3, characterized in that: Where a represents the scale parameter of the Weibull distribution, m represents the shape parameter of the Weibull distribution, γ represents the coefficient used to adjust the relationship between stress and the cumulative ringing number of acoustic emission, and N m It represents the theoretical maximum ringing number that the specimen should reach when it is completely destroyed, Nd represents the cumulative number of acoustic emission events recorded by the acoustic emission monitoring system during the loading process, and f represents the current stress level during the loading process.

5. The method for calculating transversely isotropic damage of layered rock mass according to claim 1, characterized in that: The calculation method of the total damage variable D is: D=D c +D m -D c D m 。 6. The method for calculating transversely isotropic damage of layered rock mass according to claim 1, characterized in that: The method to correct the compressive strength of rock mass is: And′=And o (1-D) Where E′ represents the corrected compressive strength of the rock mass.

7. The method for calculating transversely isotropic damage of layered rock mass according to claim 1, characterized in that: The method to correct the elastic modulus of rock mass is: G′=G o (1-D) Where G′ represents the corrected elastic modulus of the rock mass.

8. The method for calculating transversely isotropic damage of layered rock mass according to claim 1, characterized in that: The limestone rock mass samples in step a) are sub-limestone rock mass samples obtained by evenly dividing the original limestone samples using a three-dimensional grid.

9. The method for evaluating rock mass stability according to claim 8, characterized in that: The total damage variable of the original limestone sample is calculated as: Among them, D total represents the total damage variable of the original limestone sample, D i The total damage variable of the i-th sub-limestone rock mass sample obtained by uniform segmentation of the three-dimensional grid, ω i Represents the weight of the i-th sub-limestone rock mass sample.

10. The method for calculating transversely isotropic damage of layered rock mass according to claim 9, characterized in that: The calculation method of the weight of the i-th sub-limestone rock mass sample is: Among them, R i The dissolution rate of the i-th sub-limestone rock sample, V i The volume of the i-th sub-limestone rock sample.

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