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A method for judging the threshold value of rock crack stress based on full-field strain measurement

A technology of strain measurement and threshold value, which is applied in the direction of measuring devices, preparation of test samples, and application of stable tension/compression to test the strength of materials, etc. The number of strain gauges is limited and other issues, to achieve the effect of low test environment requirements, convenient results, and good applicability

Active Publication Date: 2020-08-04
INST OF ROCK & SOIL MECHANICS CHINESE ACAD OF SCI
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Problems solved by technology

[0004] Among them, the strain calculation method is to record and measure the axial strain and hoop strain generated during the sample test by attaching strain gauges on the surface of the sample or installing hoop strain gauges, and then obtain the Crack stress threshold value, the disadvantage of this method is that the number of strain gauges attached to the sample is limited, and the measurement is the local strain change data of the sample, so the obtained results may not be representative;
[0005] Among them, the acoustic emission method first installs acoustic emission probes at different positions on the surface of the sample to record the acoustic emission events during the test, and then determines the threshold value of the crack stress by analyzing the variation law of the acoustic emission events. The disadvantages of this method Yes: It is greatly affected by the noise around the test, and the heterogeneity of the microstructure of rock materials often leads to unsatisfactory test results in rock mechanics tests

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  • A method for judging the threshold value of rock crack stress based on full-field strain measurement
  • A method for judging the threshold value of rock crack stress based on full-field strain measurement
  • A method for judging the threshold value of rock crack stress based on full-field strain measurement

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Embodiment Construction

[0052] In order to make the technical means, creative features, goals and effects achieved by the present invention easy to understand, the following will further explain how the present invention is implemented in conjunction with the accompanying drawings and specific implementation methods.

[0053] refer to figure 1 As shown, a method for judging rock crack stress threshold based on full-field strain measurement provided by the present invention comprises the following steps:

[0054] S1, making rock samples;

[0055] S2, performing speckle processing on the surface of the rock sample;

[0056] S3, test loading, collecting images of the speckle surface of the rock sample during the test loading process;

[0057] S4, calculating the full-field displacement of the speckle surface of the rock sample;

[0058] S5, calculating the full-field strain of the speckle surface of the rock sample;

[0059] S6, calculating the rock sample volume strain, elastic volume strain and cr...

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Abstract

The invention discloses a method for determining a rock crack stress threshold value based on full-field strain measurement. The method comprises the following steps: manufacturing a rock sample; performing speckle treatment on the surface of the rock sample; carrying out test loading and collecting an image of a speckle surface of the rock sample in the test loading process; calculating the full-field displacement of the speckle surface of the rock sample; calculating the full-field strain of the speckle surface of the rock sample; calculating a volume strain, an elastic volume strain and a crack volume strain of the rock sample; acquiring a rock sample volume strain-axial strain curve, a crack volume strain-axial strain curve and an axial stress-axial strain curve, and drawing the curvesin the same subgraph; and determining changing rules of the volume strain of the rock sample and the crack volume strain and determining threshold values of the four crack stresses including the crack closing stress, the crack initiation stress, the crack damage stress and the peak stress of the rock sample. The method has the advantages of low requirement on test environment, more convenience inapplication, high result reliability, and higher representativeness and universality.

Description

technical field [0001] The invention relates to the field of rock mechanics characteristic testing, in particular to a method for judging the stress threshold of rock cracks based on full-field strain measurement. Background technique [0002] Under the action of external force, the rock material can obtain four different crack stress thresholds according to its stress-strain curve relationship, namely: crack closure stress σ cc , Crack initiation stress σ ci , Crack damage stress σ cd and peak stress σ p . Most scholars believe that the crack initiation stress of rock is the lower limit of long-term rock strength, while the crack damage stress is the upper limit of long-term rock strength. In actual engineering, the long-term strength of rock can be used to measure the stability of the project, so the determination and research of the above four different crack stress thresholds have a high reference value for actual engineering design. [0003] At present, there are s...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/08G01N3/06G01N1/30G01N1/28
CPCG01N1/286G01N1/30G01N3/068G01N3/08G01N2001/2866G01N2001/2873G01N2203/0019G01N2203/0062G01N2203/0066G01N2203/0067G01N2203/0075G01N2203/0676G01N2203/0682
Inventor 李海波刘黎旺李晓锋
Owner INST OF ROCK & SOIL MECHANICS CHINESE ACAD OF SCI
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