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A method for determining long-term rock strength parameters based on the Casa Grande method

A technology for long-term strength parameters and determination methods, applied in strength characteristics, using stable tension/pressure to test material strength, instruments, etc., can solve problems such as fuzzy inflection points of curves, errors, etc., to reduce data errors, reduce errors, reduce dependent effect

Active Publication Date: 2019-03-22
HOHAI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

These two types of methods have obvious limitations. When the rock creep characteristics are not obvious, the inflection point of the curve becomes blurred. Determining its position by visual inspection to obtain the long-term strength parameters of the rock will lead to a certain degree of error

Method used

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  • A method for determining long-term rock strength parameters based on the Casa Grande method
  • A method for determining long-term rock strength parameters based on the Casa Grande method
  • A method for determining long-term rock strength parameters based on the Casa Grande method

Examples

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Effect test

Embodiment 1

[0032] The invention provides a method for determining long-term rock strength parameters based on the Casa Grande method, comprising the following steps:

[0033] 1) Make samples;

[0034] A complete and defect-free red sandstone block was selected, a core was drilled with a coring machine, and the core was processed to prepare a cylindrical rock standard sample with a diameter of 50 mm and a height of 100 mm.

[0035] 2) Triaxial creep mechanics test;

[0036] Through the fully automatic triaxial rheological servo instrument and the multi-stage loading method, the triaxial creep mechanics test is carried out on the rock standard sample under the set confining pressure of 6MPa, and the triaxial creep test results are obtained; among them, The results of the triaxial creep test include the deviatoric stress values ​​at each level and the steady hoop strain rate values ​​at each level.

[0037] There is also a single-stage loading method for the triaxial creep mechanics test....

Embodiment 2

[0049] The long-term strength parameters of the rock were obtained by the traditional steady-state rate method, specifically, the preparation of the rock sample in Example 2, the steps and precautions of the triaxial creep test, and the acquisition of the steady-state hoop strain rate-stress level relationship curve The method is the same as that of Example 1, except that the method of processing the curve to obtain the long-term strength parameter is different.

[0050] like image 3 As shown, the traditional steady-state rate method extends the upper and lower straight line segments of the steady-state strain rate-stress level relationship curve to point A, and takes point A as the inflection point of the curve, then the magnitude of the partial load corresponding to the abscissa of point A 33.4MPa is used as the value of the long-term strength parameter of the red sandstone used in this implementation case under the confining pressure of 6MPa.

Embodiment 3

[0052] The long-term strength parameters of the rock are obtained by the traditional stress-strain isochrone curve method, specifically, the preparation of the rock sample in embodiment 3, the steps and precautions of the triaxial creep test are the same as in embodiment 1, the difference is that the three The method of processing the curve obtained from the shaft creep test results and the method of processing the curve to obtain the long-term strength parameters are different.

[0053] In embodiment 3, the triaxial creep test result is processed to obtain the stress-strain isochronous curve, such as Figure 4 shown. The stress-strain isochrone curve method uses the partial load at the inflection point of the isochrone curve as the long-term strength parameter. Through visual inspection, point D is determined to be the inflection point of the isochrone curve in this implementation case, and the magnitude of the partial load corresponding to its abscissa is 32.2MPa as the val...

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Abstract

The present invention discloses a rock long-term strength parameter determination method based on a Casagrande method. The rock long-term strength parameter determination method comprises: drawing a steady-state hoop strain rate-stress level relationship curve according to triaxial creep test results, extending the upper straight section and the lower straight section of the steady-state hoop strain rate-stress level relationship curve to form an angle, making the angular bisector of the angle, making the angular bisector and the steady-state hoop strain rate-stress level relationship curve intersect at a first intersection point, determining the first intersection point as the inflection point of the steady-state hoop strain rate-stress level relationship curve, and obtaining the rock long-term strength parameter based on a Casagrande method so as to achieve the purposes of exact selection of the curve intersection point and substantial reduction of the data error. According to the present invention, the method is simple and effective, and the disadvantages of unclear defined inflection point, high error and the like of the traditional rock long-term strength parameter determination method are effectively improved, wherein the long-term strength parameter determined by the method of the present invention is moderate, can be used for the rock engineering long-term stability analysis, and provides reference for the construction and the long-term operation of the project.

Description

technical field [0001] The invention relates to a method for determining long-term rock strength parameters, in particular to a method for determining long-term rock strength parameters based on the Casa Grande method, and belongs to the technical field of rock mechanics and engineering. Background technique [0002] The creep of rock refers to the relationship between the stress-strain-time of the rock. The creep mechanical properties are closely related to the long-term stability and safety of geotechnical engineering. It is one of the important properties that cannot be ignored in the study of rock mechanical properties. . The typical creep process of rock is divided into three stages: decay creep stage, steady state creep stage and accelerated creep stage. When the applied load is lower than a certain limit value, the rock will only appear in the first two stages of creep under the long-term action of the load, and the strain will eventually tend to a stable value, and ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/12
CPCG01N3/12G01N2203/0019G01N2203/0048
Inventor 王伟冯晓伟王如宾袁双双朱其志谈小龙石崇
Owner HOHAI UNIV
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