A method for testing the disturbance characteristics of a rock sample with controlled degree of breakage

Abstract

The application provides a rock sample disturbance characteristic test method for controlling the degree of rupture, comprising the following steps: S1: sample preparation; S2: true triaxial compression test loading; S3: disturbance test; S4: lower test; S5: data analysis and result analysis. The application realizes accurate simulation and test of the disturbance characteristics of the rock under different degrees of rupture by calculating the rock rupture degree index (RFD) in real time during the true triaxial compression test and accurately controlling the rupture degree of the research object. The application can complete the disturbance test of samples with different degrees of rupture on one sample, can save the cost and time of indoor test, and can reduce the influence of sample discreteness. The method can more accurately study the mechanical behavior and failure mode of the rock under different degrees of rupture, and can provide theoretical guidance for engineering practice.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics, and more specifically to a method for testing the disturbance characteristics of rock samples to control the degree of fracture. Background Technology

[0002] In the research and practice of rock mechanics and rock engineering, the mechanical response of rock samples under external disturbances has always been a focus of attention. These disturbances may originate from natural factors, such as seismic waves, or from human activities, such as blasting and drilling. These disturbances can lead to changes in the stress distribution and stress state within the rock, which may in turn affect its mechanical properties and the stability of its overall structure.

[0003] It is worth noting that in actual rock engineering, rocks often already exhibit a certain degree of fracturing. These fractures may originate from geological processes during rock formation or from stress loading histories predating engineering activities. These initial fracture states of the rock significantly influence its response to disturbances. However, current research lacks sufficient consideration and control over the degree of rock fracturing, which may lead to biases in the understanding of rock disturbance characteristics. Traditional disturbance research methods primarily focus on testing rock samples with no fracturing or low initial fracturing. However, this approach cannot fully reflect the complex fracture states of rocks in actual engineering projects. Summary of the Invention

[0004] The main objective of this invention is to provide a method for testing the disturbance characteristics of rock samples to control the degree of fracture, addressing the problems mentioned above.

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

[0006] A method for testing the disturbance characteristics of rock samples to control the degree of fracture includes the following steps:

[0007] S1: Sample preparation: Select representative rock materials, process the rock materials into standard-sized cuboid samples, perform surface treatment on the processed samples, and finally select samples with good homogeneity based on mass and wave velocity.

[0008] S2: True triaxial compression test loading: During loading, the rock fracture degree index RFD is calculated in real time. According to the research purpose, the required fracture degree is selected as the target value. The specimen is loaded to the target fracture degree, and the maximum principal stress at this time is recorded. The maximum principal stress is unloaded to the intermediate principal stress level, and the plastic strain at this time is recorded. Then, it is loaded to the recorded maximum principal stress level and the stress state is maintained for a period of time to ensure that the specimen reaches a stable fracture degree.

[0009] S3: Conduct a disturbance test: Use a true triaxial disturbance testing machine to apply surface disturbance or point disturbance to the specimen that has reached the target fracture degree to simulate the disturbance situation in actual engineering. The disturbance can be applied to the maximum principal stress loading surface, the intermediate principal stress loading surface, or the minimum principal stress loading surface. After the disturbance is applied, the specimen is loaded and unloaded once to unload the maximum principal stress to the intermediate principal stress level. Record the plastic strain at this time and calculate the rock fracture degree index RFD at this time.

[0010] S4: Conduct the next stage test: Repeat steps S2 and S3, load the specimen, and conduct a disturbance test on the specimen again under the set target fracture degree;

[0011] S5: Data Analysis and Result Analysis: Organize and analyze the experimental data, plot stress-strain curves, calculate mechanical parameters, and analyze the disturbance characteristics of rock samples under different fracture degrees.

[0012] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0013] As a preferred technical solution of the present invention: in step S1, the rock material is sandstone, granite, or marble.

[0014] As a preferred technical solution of the present invention: in step S1, the surface treatment includes grinding, cleaning and drying.

[0015] As a preferred embodiment of the present invention, the rock fracture degree index RFD is calculated by the following formula:

[0016]

[0017] In the formula, q is the generalized shear stress, which is calculated by the following formula:

[0018]

[0019] g(θ σ ) represents the plastic potential function, p represents the mean principal stress, and A, B, and C represent the failure criterion coefficients. Given the current plastic shear / tensile strain, σ1 represents the ultimate plastic shear / tensile strain, σ2 represents the maximum principal stress, σ3 represents the intermediate principal stress, and σ4 represents the minimum principal stress.

[0020] As a preferred technical solution of the present invention: In step S3, the disturbance test monitors and records the stress and displacement changes of the rock sample in real time through stress sensors and displacement sensors.

[0021] As a preferred technical solution of the present invention: in step S3, the disturbance test is monitored by ultrasonic detection and acoustic emission monitoring.

[0022] As a preferred technical solution of the present invention: in step S5, the disturbance characteristics of rock samples under different fracture degrees include the influence of fracture degree on acoustic emission characteristics, the influence of fracture degree on ultrasonic characteristics, the influence of disturbance intensity on mechanical parameters, and the influence of disturbance number on mechanical parameters.

[0023] This invention provides a method for testing the perturbation characteristics of rock samples to control the degree of fracture, which has the following advantages: This invention calculates the rock fracture degree index (RFD) in real time during a true triaxial compression test, precisely controlling the degree of fracture of the research object, thereby achieving accurate simulation and testing of the perturbation characteristics of rocks under different fracture degrees; this invention can complete perturbation tests on samples with different fracture degrees on a single specimen, saving the cost and time of indoor testing, and reducing the influence of sample dispersion; this method can not only more accurately study the mechanical behavior and failure modes of rocks under different fracture degrees, but also provide theoretical guidance for engineering practice. Attached Figure Description

[0024] Figure 1 The flowchart illustrates the rock sample disturbance characteristic testing method for controlling the degree of fracture provided by this invention.

[0025] Figure 2 This is a schematic diagram of the disturbance path in the direction of maximum principal stress.

[0026] Figure 3 This is a schematic diagram of the disturbance path in the direction of the intermediate principal stress. Detailed Implementation

[0027] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1-3 As shown, a method for testing the disturbance characteristics of rock samples to control the degree of fracture includes the following steps:

[0029] S1: Sample preparation:

[0030] Select representative rock materials, such as sandstone, granite, and marble. Use professional rock processing equipment to process the rock materials into standard-sized cuboid specimens. Perform surface treatments on the processed specimens, such as grinding, cleaning, and drying, to ensure the quality and accuracy of the specimens. Finally, select specimens with good homogeneity based on quality and wave velocity.

[0031] S2: True triaxial compression test loading:

[0032] The specimen was loaded using a true triaxial perturbation testing machine. First, three principal stresses were simultaneously applied to a preset hydrostatic pressure level (σ1 = σ2 = σ3) using a force-controlled method. Then, while keeping the minimum principal stress σ3 constant, the maximum principal stress σ1 and the intermediate principal stress σ2 were simultaneously applied to the set stress level using a force-controlled method. Finally, the maximum principal stress σ1 was applied alone. During the loading process, the rock fracture degree index was calculated in real time. Based on the research objective, the desired fracture degree was selected as the target value. The specimen was loaded to the target fracture degree, and the maximum principal stress (RFD) at this point was recorded. The maximum principal stress was then unloaded to the intermediate principal stress level, and the plastic strain at this point was recorded. The specimen was then loaded back to the recorded maximum principal stress level and held under stress for a period of time. The stability of the specimen fracture state was confirmed by acoustic emission signals and ultrasonic wave velocity fluctuations to ensure that the specimen reached a stable fracture degree.

[0033] The rock fracture degree index (RFD) is calculated using the following formula:

[0034]

[0035] In the formula, q is the generalized shear stress, which is calculated by the following formula:

[0036]

[0037] g(θ σ ) represents the plastic potential function, p represents the mean principal stress, and A, B, and C represent the failure criterion coefficients. Given the current plastic shear / tensile strain, σ1 represents the ultimate plastic shear / tensile strain, σ2 represents the maximum principal stress, σ3 represents the intermediate principal stress, and σ4 represents the minimum principal stress. The larger the RFD value, the higher the degree of rock fracture.

[0038] S3: Conduct a disturbance test:

[0039] A true triaxial perturbation testing machine is used to apply surface or point perturbations to specimens that have reached the target fracture level, simulating actual engineering perturbation conditions. The perturbation can be applied to the maximum principal stress loading surface, the intermediate principal stress loading surface, or the minimum principal stress loading surface. Simultaneously, stress and displacement sensors are used to monitor and record the stress and displacement changes of the rock specimens in real time. After the perturbation is completed, the specimen is subjected to a loading and unloading process, reducing the maximum principal stress to the intermediate principal stress level. The plastic strain at this point is recorded. Based on the plastic strain after perturbation and the current stress state, the RFD value is recalculated, and the RFD increment (ΔRFD) before and after perturbation is compared to quantify the degree of fracture propagation caused by the perturbation.

[0040] The perturbation method should be selected based on the research objective and engineering practice. For example, surface perturbation can simulate blasting and earthquakes, while point perturbation can simulate drilling and anchoring. The perturbation intensity should be determined based on the research objective and engineering practice. For example, the surface perturbation waveform can be set as: a sine wave with an amplitude of 5 MPa (corresponding to low-intensity blasting), a frequency of 5 Hz, and a duration of 10 seconds. The point perturbation should be applied at the geometric center of the sample side, using an impact probe to apply a transient pulse load. The perturbation parameters can be set as: a peak value of 4 MPa, a pulse width of 0.1 ms, and three repetitions (with a 10-second interval). The number of perturbations and the perturbation frequency should be determined based on the research objective and engineering practice.

[0041] The following monitoring methods can be used during the experiment:

[0042] Ultrasonic testing: Ultrasonic testing methods are used to test samples during disturbance, measure ultrasonic velocity and attenuation, and evaluate the impact of disturbance on the internal structure of rock samples.

[0043] The ultrasonic testing employed the P-wave transmission method (transmitter / receiver probe frequency 500kHz), acquiring the wave velocity (V) every 2 seconds. p ) and the attenuation coefficient (α), calculate the damage factor ΔV p / V p0 (Based on the initial wave velocity).

[0044] Acoustic emission monitoring: The acoustic emission signal of rock samples during disturbance is monitored using an acoustic emission monitoring system, the characteristics of acoustic emission events are analyzed, and the impact of disturbance on the fracture development of rock samples is assessed.

[0045] Acoustic emission monitoring can use the PCI-2 acoustic emission system, with a threshold of 40dB, to record event energy, ring count, and RA value (rise time / amplitude ratio) for analyzing microfracture evolution patterns.

[0046] S4: Conduct the next level test:

[0047] Repeat steps S2 and S3 to load the specimen and re-perform the perturbation test under the set target fracture degree. Apply different perturbation parameters (such as 10MPa surface perturbation and 6MPa point perturbation) to construct a multi-fracture degree-multi-perturbation coupled test matrix.

[0048] S5: Data Analysis and Results Analysis

[0049] Organize and analyze the experimental data, such as plotting stress-strain curves and calculating mechanical parameters. Analyze the disturbance characteristics of rock samples under different fracture degrees, for example:

[0050] Influence of fracture degree on acoustic emission characteristics: Analyze the variation patterns of energy, frequency, and duration of acoustic emission events in rock samples under different fracture degrees.

[0051] Influence of fracture degree on ultrasonic characteristics: Analysis of the variation law of ultrasonic velocity and attenuation of rock samples under different fracture degrees.

[0052] Influence of disturbance intensity on mechanical parameters: Analyze the variation law of mechanical parameters of rock samples under different disturbance intensities.

[0053] The effect of the number of disturbances on mechanical parameters: Analyze the variation of mechanical parameters of rock samples under different numbers of disturbances.

[0054] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for testing the disturbance characteristics of rock samples to control the degree of fracture, characterized in that, The steps include the following: S1: Sample preparation: Select representative rock materials, process the rock materials into standard-sized cuboid samples, perform surface treatment on the processed samples, and finally select samples with good homogeneity based on mass and wave velocity. S2: True triaxial compression test loading: During loading, the rock fracture degree index RFD is calculated in real time. According to the research purpose, the required fracture degree is selected as the target value. The specimen is loaded to the target fracture degree, and the maximum principal stress at this time is recorded. The maximum principal stress is unloaded to the intermediate principal stress level, and the plastic strain at this time is recorded. Then, it is loaded to the recorded maximum principal stress level and the stress state is maintained for a period of time to ensure that the specimen reaches a stable fracture degree. S3: Conduct a disturbance test: Use a true triaxial disturbance testing machine to apply surface disturbance or point disturbance to the specimen that has reached the target fracture degree to simulate the disturbance situation in actual engineering. The disturbance can be applied to the maximum principal stress loading surface, the intermediate principal stress loading surface, or the minimum principal stress loading surface. After the disturbance is applied, the specimen is loaded and unloaded once to unload the maximum principal stress to the intermediate principal stress level. Record the plastic strain at this time and calculate the rock fracture degree index RFD at this time. S4: Conduct the next stage test: Repeat steps S2 and S3, load the specimen, and conduct a disturbance test on the specimen again under the set target fracture degree; S5: Data Analysis and Result Analysis: Organize and analyze the experimental data, plot stress-strain curves, calculate mechanical parameters, and analyze the disturbance characteristics of rock samples under different fracture degrees.

2. The method for testing the disturbance characteristics of rock samples to control the degree of fracture according to claim 1, characterized in that: In step S1, the rock material is sandstone, granite, or marble.

3. The method for testing the disturbance characteristics of rock samples to control the degree of fracture according to claim 1, characterized in that: In step S1, the surface treatment includes grinding, cleaning, and drying.

4. The method for testing the disturbance characteristics of rock samples to control the degree of fracture according to claim 1, characterized in that: The rock fracture degree index RFD is calculated using the following formula: In the formula, q is the generalized shear stress, which is calculated by the following formula: g(θ σ ) represents the plastic potential function, p represents the mean principal stress, and A, B, and C represent the failure criterion coefficients. Given the current plastic shear / tensile strain, σ1 represents the ultimate plastic shear / tensile strain, σ2 represents the maximum principal stress, σ3 represents the intermediate principal stress, and σ4 represents the minimum principal stress.

5. The method for testing the disturbance characteristics of rock samples to control the degree of fracture according to claim 1, characterized in that: In step S3, the disturbance test monitors and records the stress and displacement changes of the rock sample in real time using stress sensors and displacement sensors.

6. The method for testing the disturbance characteristics of rock samples to control the degree of fracture according to claim 1, characterized in that: In step S3, the disturbance test is monitored by ultrasonic detection and acoustic emission monitoring.

7. The method for testing the disturbance characteristics of rock samples to control the degree of fracture according to claim 1, characterized in that: In step S5, the disturbance characteristics of rock samples under different fracture degrees include the influence of fracture degree on acoustic emission characteristics, the influence of fracture degree on ultrasonic characteristics, the influence of disturbance intensity on mechanical parameters, and the influence of the number of disturbances on mechanical parameters.

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