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Rock brittleness index evaluation method based on full stress-strain curve

A technology of strain curve and rock brittleness, applied in the field of rock mechanics, can solve problems such as only applicable, cumbersome methods, errors, etc., to achieve the effect of strong pertinence, simple operation, and improved rationality and accuracy

Active Publication Date: 2017-06-30
CHENGDU UNIVERSITY OF TECHNOLOGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, scholars at home and abroad have not yet formed a unified evaluation standard for rock brittleness. For example, a method for determining the brittleness index based on coal and rock industrial components disclosed in Patent No. 201410461329.8 uses coal and rock industrial components combined with logging data to determine the brittleness index. The method is cumbersome and can only be applied to the gas field. Patent No. 201310254628.X discloses a method for measuring the brittleness index of rocks using acoustic emission energy values. Due to the large randomness of rock acoustic emission energy values, the test results are unstable. , has a large error, but because the brittleness of rock is closely related to its mechanical properties, the study of the mechanical properties of the rock mass in its environment can achieve an accurate evaluation of the brittleness index

Method used

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  • Rock brittleness index evaluation method based on full stress-strain curve
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Examples

Experimental program
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Effect test

Embodiment 1

[0025] Evaluate the brittleness index of marble, sandstone, coarse-grained granite, and fine-grained granite exposed on the surface, such as figure 1 As shown, the method for calculating the brittleness index provided by the embodiments of the present invention includes the following steps:

[0026] Evaluate the geological environment of the four rocks: the surface is exposed, the stress is small, and there is no influence of temperature, water pressure, etc.;

[0027] Due to the simple geological environment of the rock sample, the uniaxial compression experiment was selected. The experimental loading system adopts three-stage control. At the beginning of the experiment, the axial displacement control is adopted. When the axial pressure reaches 70% of the peak strength, it is switched to the circumferential displacement. Control, the circumferential displacement rate increases step by step, the initial setting value is 0.0025mm / s, when the curve reaches the peak value and beg...

Embodiment 2

[0036] Evaluate the brittleness index of marble at 20°C, 40°C, 60°C, and 90°C, such as figure 1 As shown, the method for calculating the brittleness index provided by the embodiments of the present invention includes the following steps:

[0037] Evaluate the geological environment of rocks at four temperatures: rocks with high geothermal temperature are generally buried deep underground, with large in-situ stress and no influence of water pressure;

[0038] The triaxial compression test is selected, and the confining pressure is 20MPa due to the large ground stress;

[0039] The characteristic stress values ​​obtained during the experiment and their corresponding strains are shown in Table 2. The characteristic stress values ​​include crack initiation stress, peak stress, and residual stress;

[0040] Concrete characteristic stress value and strain value thereof of table 2 embodiment two

[0041]

[0042] The calculation method of brittleness index with consideration of ...

Embodiment 3

[0046] Evaluate the brittleness index of marble under water pressure of 0MPa, 4MPa, 8MPa and 12MPa, such as figure 1 As shown, the method for calculating the brittleness index provided by the embodiments of the present invention includes the following steps:

[0047]Evaluate the geological environment of rocks under four kinds of water pressure: rocks with high water pressure are generally buried deep underground, with abundant groundwater, large in-situ stress, and no temperature influence;

[0048] The triaxial compression test is selected, and the confining pressure is 20MPa due to the large ground stress;

[0049] The characteristic stress values ​​obtained during the experiment and their corresponding strains are shown in Table 3. The characteristic stress values ​​include crack initiation stress, peak stress, and residual stress;

[0050] Concrete characteristic stress value and strain value thereof of table 3 embodiment three

[0051]

[0052] Bring into the calcul...

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Abstract

The invention discloses a rock brittleness index evaluation method based on a full stress-strain curve. The method comprises steps as follows: the geological environment where a to-be-measured rock sample is located is evaluated in the aspects of ground stress, temperature, water pressure and the like; rock mechanics experiments meeting the geological environment where the to-be-measured rock sample is located are selected and include an uniaxial compression experiment, a triaxial compression experiment with the temperature taken into consideration and a triaxial compression experiment with the water pressure taken into consideration; characteristic stress values and corresponding strain of the characteristic stress values in the experiment process are acquired; the characteristic stress values and the strain are taken in for calculation according to a proposed brittleness index calculation method, and the brittleness index of to-be-measured rock is obtained. The method is a comprehensive brittleness index calculation method aiming at the geological environment where the to-be-measured rock sample is located and based on the whole process of the rock mechanics experiments, and the reasonability and the accuracy of rock brittleness evaluation are improved.

Description

technical field [0001] The invention relates to the technical field of rock mechanics, in particular to a rock brittleness index evaluation method based on a full stress-strain curve. Background technique [0002] Brittleness is the failure of rocks under extremely small deformation conditions and releases a large amount of energy. Deep rock masses generally have relatively high brittleness, and are often accompanied by harsh environments with high ground temperature and high water pressure. As a very important property of rock, brittleness evaluation has important guiding significance for rock mass engineering. For example, in deep rock mass engineering under high ground stress, the brittleness of rock mass is an important internal factor affecting engineering disasters such as rockburst; brittleness The index is also an important index for reservoir mechanical characteristics, wellbore stability evaluation and hydraulic fracturing effect evaluation in the field of oil and ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/12
CPCG01N3/12G01N2203/0019G01N2203/0048
Inventor 陈国庆赵聪刘顶李天斌
Owner CHENGDU UNIVERSITY OF TECHNOLOGY
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