Rock long-term strength parameter determination method based on Casagrande method

A technology of long-term strength parameters and determination methods, which is applied in the determination of long-term strength parameters of rocks, and the determination of long-term strength parameters of rocks based on the Casagrande method. Error, choose clear effect

Active Publication Date: 2017-06-30
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

Method used

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  • Rock long-term strength parameter determination method based on Casagrande method
  • Rock long-term strength parameter determination method based on Casagrande method
  • Rock long-term strength parameter determination method based on Casagrande method

Examples

Experimental program
Comparison scheme
Effect test

Example Embodiment

[0031] Example 1:

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

[0033] 1) Make samples;

[0034] A complete and defect-free red sandstone block is selected, the core is drilled with a coring machine, and the core is 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 automatic three-axis rheological servo instrument, the multi-stage gradual loading method is adopted to carry out the triaxial creep mechanics test 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 deviator stress values ​​and the steady-state hoop strain rate values.

[0037] The loading method of the triaxial creep mechanics test is also single-stage loading. Si...

Example Embodiment

[0048] Example 2:

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

[0050] Such as 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. Taking point A as the inflection point of the curve, 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 case at a confining pressure of 6MPa.

Example Embodiment

[0051] Example 3:

[0052] The traditional stress-strain isochron curve method is used to obtain the long-term strength parameters of the rock. Specifically, in the preparation of the rock sample in Example 3, the steps and precautions of the triaxial creep test are the same as those in Example 1. The difference lies in the comparison of the three The curve obtained by processing the results of the shaft creep test and the method of processing the curve to obtain the long-term strength parameters are different.

[0053] In Example 3, the results of the triaxial creep test were processed to obtain the stress-strain isochronous curve, such as Figure 4 Shown. The stress-strain isochronous curve method takes the magnitude of the eccentric load at the inflection point of the isochronous curve as the long-term strength parameter. Through visual inspection, point D is determined as the inflection point of the isochronous curve in this case, and the eccentric load corresponding to its a...

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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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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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