A method for constructing a damage constitutive model to analyze the damage evolution of easily argillaceous rocks.

Abstract

A method for constructing a damage constitutive model to analyze the damage evolution of easily argillaceous rocks includes: preparing ore specimens; conducting acoustic emission tests on the ore specimens under uniaxial compression; obtaining the displacement, load, and acoustic emission parameters of each specimen; calculating and analyzing the characteristic stresses of easily argillaceous rocks under uniaxial compression; revealing the evolution characteristics of acoustic emission parameters under uniaxial compression; defining the damage variables at different characteristic stress stages; and constructing a damage constitutive model of the entire stress-strain process of easily argillaceous rocks. This method can accurately and comprehensively quantitatively analyze the strength evolution characteristics of easily argillaceous rocks under uniaxial compression, monitor the damage evolution characteristics and damage degree of easily argillaceous rocks in real time, and provide a reference for maintaining the stability of underground goaf areas in mines.

Description

Technical Field

[0001] This invention relates to a quantitative analysis method for rock damage and strength in mines, specifically a method for constructing a damage constitutive model to analyze the damage evolution of easily mud-forming rocks. Background Technology

[0002] Easily argillaceous rocks are typical porous media materials, and the evolution of their internal fractures and pores—that is, the evolution of damage—significantly affects the changes in rock strength. Therefore, quantitative analysis of the damage evolution of easily argillaceous rocks can help understand the relationship between strength evolution and damage development under load, reveal the intrinsic laws governing damage development and acoustic emission parameter evolution, and further understand the strength characteristics of easily argillaceous rocks. This has scientific guiding significance for maintaining the stability of underground goaf areas in mines.

[0003] Underground mining is influenced by geological conditions. The underground environment is humid and has a high water content. Some rock masses absorb water and easily become muddy, resulting in weakened physical and mechanical properties. This leads to a decrease in the strength of the surrounding rock and has a significant impact on the stability of the mining area structure, seriously endangering the safety of personnel and property during the mining process. Currently, there are two methods for quantitative analysis of damage evolution in rock-like materials: methods based on classical theory and experimental measurement methods. Among them, the method based on classical theory applies well-established existing theories such as the law of conservation of energy, Weibull distribution, Hooke's law, and Mohr-Coulomb criterion. After modification for different rocks and stress paths, the damage evolution is quantitatively analyzed, and a damage constitutive model of the rock material is established. The damage variables and constitutive models established by this method can reflect the damage evolution characteristics of rocks well, but they have certain limitations, such as assuming that the initial damage of the rock specimen is 0, which does not match the actual rock material (and its internal structure). Experimental measurement methods refer to the use of experimental means such as CT, scanning electron microscopy, and microscopy to quantitatively describe the microscopic damage inside the material. They can only quantitatively analyze the microstructure of each cross section of the material, and it is difficult to determine the development and changes of cracks inside the material. They also cannot observe the damage evolution of the stress-strain process in real time, which has certain limitations. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a segmented representation of damage variables for easily argillaceous rocks at different characteristic stress stages, establishes the relationship between acoustic emission parameters and damage evolution of easily argillaceous rocks, and can accurately and comprehensively analyze the damage evolution of easily argillaceous rocks, obtain the stress-strain relationship of easily argillaceous rocks throughout the entire loading process, reveal the intrinsic connection between damage evolution and strength characteristics of easily argillaceous rocks, and provide a scientific reference for quantifying the damage evolution of easily argillaceous rocks in mining.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for constructing a damage constitutive model to analyze the damage evolution of easily argillaceous rocks includes the following steps:

[0007] Step 1: Prepare mineral and rock specimens, wherein the mineral and rock specimens are easily mud-forming mineral and rock specimens;

[0008] Step 2: Conduct acoustic emission tests under uniaxial compression conditions on the minerals and rocks described in Step 1, and obtain the axial displacement, load, and acoustic emission parameter values ​​of each mineral and rock specimen;

[0009] Step 3: Calculate and analyze the evolution characteristics of characteristic stress and acoustic emission parameters of easily mud-forming ore rocks under uniaxial compression;

[0010] Step 4: Based on the modified acoustic emission ringing count, a damage constitutive model of easily mud-forming rocks under uniaxial compression conditions is constructed. The specific process is as follows:

[0011] The stress-strain curve of rock-like materials can be divided into four stages before the peak value: the initial fracture compaction stage, the elastic deformation stage, the stable fracture propagation stage, and the unstable fracture propagation stage. Each stage can be represented by characteristic stresses, namely, the compaction stress σ at fracture closure. cc Cracking stress σ ci Damage stress σ cd and peak stress σ f The characteristic stresses can be obtained through the fracture volumetric strain method and numerical calculation. According to the generalized Hooke's law, the relationship between stress and strain of an object under load can be expressed by the following formula:

[0012]

[0013] In the formula: σ1, σ2, and σ3 are the principal stresses in the three directions, with units of MPa; ε1, ε2, and ε3 are the strains in the directions corresponding to the three principal stresses; E is the elastic modulus, with units of MPa; μ is Poisson's ratio;

[0014] This paper uses real strain ε v Instead of virtual volumetric strain, crack volumetric strain can be obtained. for:

[0015]

[0016] Furthermore, the crack volumetric strain under uniaxial compression conditions can be obtained as:

[0017]

[0018] Equations (1) and (3) can be used to obtain the volumetric strain curves of easily mud-forming rocks under uniaxial compression and the volumetric strain curves of cracks. The crack initiation stress σ can be obtained according to the definition of the crack volumetric strain method. ci and damage stress σ cd The closing stress σ cc Further numerical calculations are needed to obtain the stress-strain relationship in the elastic stage; therefore, the stress-strain relationship in the elastic stage can be approximated by the following formula:

[0019] σ=Eε+a (4)

[0020] In the formula: σ is the axial stress, in MPa; ε is the axial strain; E is the elastic modulus under the actual condition, in MPa; a is the intercept of the linear function on the σ axis; by using the crack initiation stress σ ci and the corresponding strain ε ci Substituting into equation (4), the value of a can be obtained. The stress at the first intersection of the linear function line of equation (4) and the stress-strain curve can be approximated as the compaction stress σ at crack closure. cc .

[0021] Furthermore, in step four, a damage constitutive model for the entire stress-strain process of easily argillaceous rocks under uniaxial compression is constructed based on the damage variable of the modified acoustic emission ringing count. Specifically, the acoustic emission ringing count is used to quantitatively analyze the damage to the easily argillaceous rocks, and the damage variable is segmented for different characteristic stress stages. Therefore, the damage variable can be expressed as:

[0022]

[0023] In the formula: D i R represents the damage variable of the rock sample at time i of the experiment. i To accumulate the acoustic emission ringing count at time i of the experiment, R cc R is the sum of the acoustic emission ring counts during the compaction stage. d ε is the cumulative acoustic emission ringing count before residual stress. cc ε represents the strain of the specimen at the end of the compaction stage. ci Let be the strain corresponding to the initiation stress. The equivalent elastic modulus of the rock sample at time i can then be obtained. for:

[0024] E ％ =(1-D i E (6)

[0025] In the formula: E is the true elastic modulus of the specimen measured in the experiment, in MPa. The equivalent elastic modulus is expressed in MPa. Combining equations (5) and (6), and based on the mechanics of equivalent continuum, a damage constitutive model for the stress-strain transition time under uniaxial compression of easily mud-forming ore rocks can be obtained, which is expressed as follows:

[0026]

[0027] In the formula: β is the elastic modulus degradation coefficient defined considering the weakening effect of easily mud-forming rocks. It is calculated from experimental data. When β = 0.41, the theoretical stress-strain curve and the experimental stress-strain curve are in best agreement. Therefore, equation (7) can be simplified to:

[0028]

[0029] According to equation (5), the damage of easily mud-forming rocks under uniaxial compression can be quantitatively calculated and analyzed. According to equation (8), the theoretical stress-strain relationship of easily mud-forming rocks can be obtained.

[0030] Furthermore, the easily mud-forming rock specimen mentioned in step one is a standard cylindrical rock with a height of 100 mm and a diameter of 50 mm.

[0031] Furthermore, the acoustic emission test in step two adopts a loading strain test with a loading rate of 0.005 mm / s. Loading is stopped when the specimen fails. The acoustic emission sampling threshold is 50 dB, the preamplifier gain is 45 dB, and the sampling rate is 3 MSPS.

[0032] Furthermore, the calculation and analysis of the evolution characteristics of characteristic stress and acoustic emission parameters of easily mud-forming ore rocks under uniaxial compression in step three includes: the ratio of compaction stress to peak stress is σ. cc / σ f =0.37±0.02, the ratio of the initiation stress to the peak stress is σ ci / σ f =0.49±0.01, the ratio of damage stress to peak stress is σ cd / σ f =0.82±0.04. The evolution of acoustic emission parameters of easily mud-forming rocks under uniaxial compression can be divided into the compaction stage, elastic stage, stable crack propagation stage, unstable crack propagation stage, and post-peak stage.

[0033] The beneficial effects of this invention are:

[0034] This invention represents the damage variables of easily argillaceous rocks in segments according to different characteristic stress stages. Combining the evolution characteristics of acoustic emission parameters, it defines damage variables based on modified acoustic emission ringing counts for different characteristic stress stages, comprehensively simulating the internal damage variation law of easily argillaceous rocks. It can accurately calculate and analyze the degree of damage within easily argillaceous rocks. By combining the damage variables of different characteristic stress stages with the stress-strain relationship, a damage constitutive model for easily argillaceous rocks under uniaxial compression conditions is established. The rationality and accuracy of this constitutive model are verified by comparison with experimental stress-strain curves. The method of this invention can accurately and in real-time monitor and analyze the intrinsic relationship between damage evolution and strength characteristics of easily argillaceous rocks, providing a scientific reference for quantifying the internal damage evolution and monitoring the strength characteristics of easily argillaceous rocks during mining. Attached Figure Description

[0035] Figure 1 This is a typical stress-strain diagram of an easily mud-forming rock specimen according to an embodiment of the present invention;

[0036] Figure 2a This is a stress-acoustic emission ringing count-time relationship diagram for easily mud-forming rock specimen a in an embodiment of the present invention;

[0037] Figure 2b This is a stress-acoustic emission event rate-time relationship diagram for easily mud-forming rock specimen a in an embodiment of the present invention;

[0038] Figure 2c This is a stress-acoustic emission energy rate-time relationship diagram for easily mud-forming rock specimen a in an embodiment of the present invention;

[0039] Figure 3a This is a stress-acoustic emission ringing count-time relationship diagram for easily mud-forming rock specimen b in an embodiment of the present invention;

[0040] Figure 3b This is a stress-acoustic emission event rate-time relationship diagram for easily mud-forming rock specimen b in an embodiment of the present invention;

[0041] Figure 3c This is a stress-acoustic emission energy rate-time relationship diagram for easily mud-forming rock specimen b in an embodiment of the present invention;

[0042] Figure 4a This is a stress-acoustic emission ringing count-time relationship diagram for easily mud-forming rock specimen c in an embodiment of the present invention;

[0043] Figure 4b This is a stress-acoustic emission event rate-time relationship diagram for easily mud-forming rock specimen c in an embodiment of the present invention;

[0044] Figure 4c This is a stress-acoustic emission energy rate-time relationship diagram for easily mud-forming rock specimen c in an embodiment of the present invention;

[0045] Figure 5a This is a diagram showing the theoretical stress-test stress relationship of easily mud-forming rock specimen a in an embodiment of the present invention;

[0046] Figure 5b This is a diagram showing the theoretical stress-test stress relationship of easily mud-forming rock specimen b in an embodiment of the present invention.

[0047] Figure 5c This is a diagram showing the theoretical stress-experimental stress relationship of easily mud-forming rock specimen c in an embodiment of the present invention; Detailed Implementation

[0048] A method for constructing a damage constitutive model to analyze the damage evolution of easily argillaceous rocks includes the following steps:

[0049] Step 1: Prepare mineral and rock specimens, wherein the mineral and rock specimens are easily mud-forming mineral and rock specimens;

[0050] The ore used in this embodiment was taken from a thick tantalum-niobium ore rock in southern Jiangxi that is prone to mudification. Fresh rock samples were taken from a depth of 200m underground. After being cored in January 2014, the rock samples were placed in the natural environment on the surface and allowed to absorb water and weather for 7 years. The samples were then made into standard cylindrical specimens with a height of about 100mm and a diameter of about 50mm.

[0051] Step 2: Conduct acoustic emission tests under uniaxial compression conditions on the mineral and rock specimens described in Step 1, and obtain the axial displacement, load, and acoustic emission parameter values ​​for each specimen. Select easily mud-forming mineral and rock specimens a, b, and c from Step 1, whose surfaces have no obvious joints or cracks, and conduct tests on them respectively. Plot the stress-acoustic emission ringing count-time relationship diagram, the stress-acoustic emission event rate-time relationship diagram, and the stress-acoustic emission ringing count-time relationship diagram respectively.

[0052] like Figure 2a , Figure 2b , Figure 2c , Figure 3a , Figure 3b , Figure 3c , Figure 4a , Figure 4b , Figure 4c As shown, the acoustic emission parameters of easily mud-forming rocks under uniaxial compression conditions show an increasing trend with increasing stress. The acoustic emission parameter characteristics at different characteristic stress stages are quite different, indicating that the damage evolution characteristics of easily mud-forming rocks are different at different characteristic stress stages.

[0053] Step 3: Calculate and analyze the evolution characteristics of characteristic stress and acoustic emission parameters of easily mud-forming ore rocks under uniaxial compression;

[0054] The stress-strain curve of rock-like materials can be divided into four stages before the peak value: the initial fracture compaction stage, the elastic deformation stage, the stable fracture propagation stage, and the unstable fracture propagation stage. Each stage can be represented by characteristic stresses, namely, the compaction stress σ at fracture closure. cc Cracking stress σ ci Damage stress σ cd and peak stress σ f The characteristic stresses can be obtained through the fracture volumetric strain method and numerical calculation. According to the generalized Hooke's law, the relationship between stress and strain of an object under load can be expressed by the following formula:

[0055]

[0056] In the formula: σ1, σ2, and σ3 are the principal stresses in the three directions, with units of MPa; ε1, ε2, and ε3 are the strains in the directions corresponding to the three principal stresses; E is the elastic modulus, with units of MPa; μ is Poisson's ratio;

[0057] This invention uses real strain ε v Instead of virtual volumetric strain, crack volumetric strain can be obtained. for:

[0058]

[0059] Furthermore, the crack volumetric strain under uniaxial compression conditions can be obtained as:

[0060]

[0061] Equations (1) and (3) can be used to obtain the volumetric strain curves of easily mud-forming rocks under uniaxial compression and the volumetric strain curves of cracks. The crack initiation stress σ can be obtained according to the definition of the crack volumetric strain method. ci and damage stress σ cd The closing stress σ cc Further numerical calculations are needed to obtain the stress-strain relationship in the elastic stage; therefore, the stress-strain relationship in the elastic stage can be approximated by the following formula:

[0062] σ=Eε+a (4)

[0063] In the formula: σ is the axial stress, in MPa; ε is the axial strain; E is the elastic modulus under the actual condition, in MPa; a is the intercept of the linear function on the σ axis; by using the crack initiation stress σ ci and the corresponding strain ε ci Substituting into equation (4), the value of a can be obtained. The stress at the first intersection of the linear function line of equation (4) and the stress-strain curve can be approximated as the compaction stress σ at crack closure. cc .

[0064] like Figure 1 As shown, based on the characteristics of volumetric strain and fracture volumetric strain variation under uniaxial compression of easily argillaceous rocks, and combined with numerical calculations of linear functions, the characteristic stresses under uniaxial compression of easily argillaceous rocks can be obtained. Characteristic stress analysis of typical samples is shown in Table 1.

[0065] Table 1 Characteristic stresses at different stages in easily mud-forming rock specimens

[0066]

[0067] Observing the data in Table 1, it can be seen that the relationship between the same characteristic stress and peak stress of different easily mud-forming rock samples is relatively close, which indirectly reflects the strong rationality of the ratio of each characteristic stress to the peak stress. The variation range of the ratio of the same characteristic stress to the peak stress of different samples is small. Among them, the ratio of the compaction stress of fracture closure to the peak stress is σ. cc / σ f =0.37±0.02, the ratio of the initiation stress to the peak stress is σ ci / σ f =0.49±0.01, the ratio of damage stress to peak stress is σ cd / σ f =0.82±0.04.

[0068] The acoustic emission ring count and energy rate exhibit a clear calm period before the stress peak, showing relatively weak fluctuations. However, near the stress peak, the ring count and energy rate increase sharply, generating a large number of acoustic emission events inside the specimen. This leads to accelerated crack propagation, concentrated penetration, and the specimen losing its load-bearing capacity, resulting in instability and failure.

[0069] The acoustic emission parameter curves were divided into five stages according to characteristic stress: compaction stage (OA segment), elastic stage (AB segment), stable crack propagation stage (BC segment), and post-peak stage (DE segment). Analysis of the acoustic emission parameter-time curves and stress-time curves of easily argillaceous rocks revealed a strong correlation between the acoustic emission parameter curves and the stress curves. Among these, the acoustic emission event rate-time curve was more effective in describing characteristic stress.

[0070] Step 4: Based on the modified acoustic emission ringing count, a damage constitutive model of easily mud-forming rocks under uniaxial compression conditions is constructed. The specific process is as follows:

[0071] It is well known that the degradation of the elastic modulus caused by weakening of easily argillaceous rocks not only affects the damage evolution during the initial compaction stage, but also has a significant impact on the damage and strain changes of the specimens after peak stress. Therefore, it is necessary to conduct quantitative analysis of the stress-strain curves of easily argillaceous rocks throughout the entire time period.

[0072] Analysis of Figures 2, 3, and 4 shows that acoustic emission ringing count exhibits stronger stage-specific characteristics and a better correlation with characteristic stress. Therefore, to more reasonably analyze the damage evolution characteristics of easily argillaceous rocks under uniaxial compression, acoustic emission ringing count is selected for quantitative analysis of the damage evolution of easily argillaceous rocks. Thus, the damage variable can be expressed as:

[0073]

[0074] In the formula: D i R represents the damage variable of the rock sample at time i of the experiment. i To accumulate the acoustic emission ringing count at time i of the experiment, R cc R is the sum of the acoustic emission ring counts during the compaction stage. d ε is the cumulative acoustic emission ringing count before residual stress. cc ε represents the strain of the specimen at the end of the compaction stage. ci Let be the strain corresponding to the initiation stress. The equivalent elastic modulus of the rock sample at time i can then be obtained. for:

[0075] E ％ =(1-D i E (6)

[0076] In the formula: E is the true elastic modulus of the specimen measured in the experiment, in MPa. The equivalent elastic modulus is expressed in MPa. Combining equations (5) and (6), and based on the mechanics of equivalent continuum, a damage constitutive model for the stress-strain transition time under uniaxial compression of easily mud-forming ore rocks can be obtained, which is expressed as follows:

[0077]

[0078] In the formula: β is the elastic modulus degradation coefficient defined considering the weakening effect of easily mud-forming rocks, which is calculated from experimental data. When β = 0.41, the theoretical stress-strain curve and the experimental stress-strain curve are in best agreement. Therefore, equation (7) is simplified to:

[0079]

[0080] According to equation (5), the damage of easily mud-forming rocks under uniaxial compression can be quantitatively calculated and analyzed. According to equation (8), the theoretical stress-strain relationship of easily mud-forming rocks can be obtained.

[0081] from Figure 5a , Figure 5b and Figure 5cIt can be seen that the theoretical stress-strain curve obtained by the constitutive model is slightly larger than the experimental curve in the initial compaction stage and the post-peak stage, and slightly smaller than the experimental curve in the elastic stage and the plastic deformation stage, but the variation trend of the theoretical curve and the experimental curve is the same. Therefore, it can be concluded that the constitutive model established in this paper can quantitatively describe the evolution characteristics of the strength of easily argillaceous rocks with strain.

[0082] Depend on Figure 5a , Figure 5b and Figure 5c It can be seen that the stress-strain curves of easily mud-forming rocks under uniaxial compression conditions can be roughly divided into four stages: The first stage is segment OA. In this stage, due to the presence of numerous initial fractures, the axial strain at the end of this stage accounts for approximately half of the total strain. The theoretical stress-strain curve in this stage is above the experimental stress-strain curve because the equivalent elastic modulus is smaller than the true elastic modulus, reflecting the strong fluctuation in damage evolution and low stability of elastic modulus changes in this stage. The second stage is segment AB, where the theoretical stress-strain curve nearly coincides with the experimental stress-strain curve. Theoretically, no new fractures are generated in this stage, the damage variable is close to zero, and the elastic modulus remains constant. The stress-strain curve in this stage is continuous and stable at the junction with the preceding and following stages. The third stage is segment BD, which is the stage of accelerated fracture propagation. The rate of increase in damage within the sample is unstable, therefore the elastic modulus change is also in a stage of strong fluctuation. The theoretical stress-strain curve for this stage is slightly smaller than the experimental curve because the theoretical value of the elastic modulus is lower than the actual value due to the influence of the unclosed cracks in the initial stage, resulting in a slightly smaller theoretical curve. The fourth stage is segment DE, where the sample strength decreases rapidly after the stress peak, and internal damage accelerates its generation, propagation, and penetration. During this stage, the local load-bearing capacity of the sample decreases rapidly. By constructing constitutive models for different characteristic stress stages of easily argillaceous rocks, a segmented damage constitutive model of the entire uniaxial compression process of easily argillaceous rocks can be obtained, along with continuous theoretical stress-strain curves. The theoretical stress-strain curves agree well with the experimental stress-strain curves, indirectly reflecting that the damage development of easily argillaceous rocks is a gradual and continuous process.

[0083] This invention establishes damage variables under uniaxial compression conditions for easily argillaceous rocks by introducing acoustic emission ringing counts, and constructs a damage constitutive model of the entire loading process of easily argillaceous rocks based on acoustic emission ringing counts. Through these damage variables and the damage constitutive model, the damage evolution and strength characteristics of easily argillaceous rocks under uniaxial compression can be analyzed quickly and accurately, providing assistance in maintaining the stability of underground goaf areas in mines. The above-disclosed embodiments are merely preferred embodiments of the invention and should not be construed as limiting the scope of the invention. Therefore, equivalent variations made within the scope of this invention are still within the scope of this invention.

Claims

1. A method for constructing a damage constitutive model to analyze the damage evolution of easily argillaceous rocks, characterized in that, Includes the following steps: Step 1: Prepare mineral and rock specimens, wherein the mineral and rock specimens are easily mud-forming mineral and rock specimens; Step 2: Conduct acoustic emission tests under uniaxial compression conditions on the mineral and rock specimens described in Step 1, and obtain the axial displacement, load, and acoustic emission parameter values ​​for each mineral and rock specimen; Step 3: Calculate and analyze the evolution characteristics of characteristic stress and acoustic emission parameters of easily mud-forming ore rocks under uniaxial compression; Step 4: Define the damage variable for easily mud-forming rocks based on the modified acoustic emission ringing count, and construct a damage constitutive model for easily mud-forming rocks under uniaxial compression conditions. The specific process is as follows: The stress-strain curve of rock-like materials is divided into four stages before the peak: the initial fracture compaction stage, the elastic deformation stage, the stable fracture propagation stage, and the unstable fracture propagation stage. Each stage is represented by characteristic stresses, which are the compaction stresses at fracture closure. Cracking stress Damage stress and peak stress The characteristic stresses were obtained through the fracture volumetric strain method and numerical calculation. The relationship between stress and strain of the object under load is expressed by the following formula: ， ， ， Based on Equation (5), the damage evolution of easily mud-forming rocks under uniaxial compression is quantitatively calculated and analyzed. Based on Equation (8), the theoretical stress-strain relationship of easily mud-forming rocks can be obtained.

2. The method for constructing a damage constitutive model to analyze the damage evolution of easily argillaceous rocks according to claim 1, characterized in that, The mineral specimen mentioned in step one is a standard cylindrical rock with a height of 100 mm and a diameter of 50 mm.

3. The method for constructing a damage constitutive model to analyze the damage evolution of easily argillaceous rocks according to claim 1, characterized in that, The acoustic emission test described in step two adopts a loading strain test with a loading rate of 0.005 mm / s. Loading is stopped when the specimen fails. The acoustic emission sampling threshold is 50 dB, the preamplifier gain is 45 dB, and the sampling rate is 3 MSPS.

4. The method for constructing a damage constitutive model to analyze the damage evolution of easily argillaceous rocks according to claim 1, characterized in that, Step three involves calculating and analyzing the evolution characteristics of characteristic stresses and acoustic emission parameters under uniaxial compression of easily mud-forming rocks, including the ratio of compaction stress to peak stress. The ratio of the initiation stress to the peak stress is The ratio of damage stress to peak stress is The evolution of acoustic emission parameters under uniaxial compression of easily mud-forming rocks can be divided into the compaction stage, elastic stage, stable crack propagation stage, unstable crack propagation stage, and post-peak stage.

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