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A Method of Improving Burgers Rock Shear Creep Model

A rock and model technology, applied in the direction of testing the ductility of materials, instruments, measuring devices, etc., can solve the problems of weakness, rock mass shear strength attenuation, etc., and achieve the effect of simple model parameters and clear physical and mechanical meanings

Active Publication Date: 2021-04-30
CENT SOUTH UNIV
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  • Abstract
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  • Application Information

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Problems solved by technology

[0004] The above models describe the nonlinearity of rock mass creep well, but it is generally believed that the rock shear strength does not change with time. In fact, during the creep process, due to the time-sensitive accumulation of microscopic damage, the rock mass shear decays over time, and decays to a minimum value upon final destruction

Method used

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  • A Method of Improving Burgers Rock Shear Creep Model
  • A Method of Improving Burgers Rock Shear Creep Model
  • A Method of Improving Burgers Rock Shear Creep Model

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0067] S1. Aiming at the time difference of rock shear strength in the creep state, construct a nonlinear element which is composed of a plastic element and a viscous element in parallel to describe the mechanical properties of the rock in the accelerated creep stage (such as figure 2 shown), where the plastic component parameter τ d It represents the actual shear strength of the rock, and its value changes with time. The viscous element represents the shear strain rate of the rock, and the parameter η is linearly constant.

[0068] refer to figure 1 , the creep process can be divided into three stages: I—attenuation creep stage, II—stable creep stage, III—accelerated creep stage. When the external load exceeds the yield strength of the rock, internal micro-cracks begin to initiate and develop, causing damage over time and deterioration of continuity, resulting in the shear strength τ d Constantly decaying. When the external stress τ exceeds the long-term strength of the r...

Embodiment 2

[0121] Embodiment 2 Test example verification

[0122] Substituting the laboratory test data into the constitutive equation of the improved Burgers modelγ B (t), and determine its long-term strength τ s , the validity and rationality of the model are verified by experiments, and the rock microscopic damage characteristics are obtained through the inversion parameter δ.

[0123] In order to verify the rationality of the improved Burgers model proposed by the present invention, a sandstone sample is selected for indoor creep shear test. The sample size is 10cm×10cm×10cm. The specific mechanical parameters are shown in Table 1. According to other tests on sandstone, it can be known that the long-term shear strength under the normal stress condition of 1.56MPa is 2.8-3MPa. In order to obtain the test curve including the accelerated creep stage, the loading shear stress is set to be 3.36MPa greater than the long-term shear strength.

[0124] Table 1 Sandstone material parameters ...

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Abstract

The invention discloses a method for improving the Burgers rock shear creep model, which includes the following steps: S1. Aiming at the time difference of the rock shear strength in the creep state, construct a parallel connection of a plastic element and a viscous element Nonlinear elements describing the mechanical properties of rocks during accelerated creep; S2, using Kachanov’s law, which is widely used in the field of rheology, to describe the aging damage function D(t) of rock during accelerated creep; S3, based on the aging damage function D(t) , to determine the shear strength τ d The concrete expression τ d (t); S4, the residual strength τ r Introducing the shear strength function τ d (t), construct the modified shear strength function τ considering the residual strength d (t); S5, will modify the shear strength function τ d (t) into the nonlinear element in step S1 to determine the constitutive equation γ(t) of the element; S6, introduce the constitutive equation γ(t) of the element into the constitutive equation of the classic Burgers model to obtain an accurate reflection of the mechanical behavior of the entire creep process The modified Burgers model constitutive equation of γ B (t).

Description

technical field [0001] The invention belongs to the technical field of engineering, and in particular relates to a method for improving the Burgers rock shear creep model. Background technique [0002] Creep is an important mechanical property of rock, which affects the long-term stability of rock mass engineering. The stress and deformation characteristics obtained from the perspective and method of rock mass rheology are in good agreement with the actual situation. Therefore, the study of rock creep characteristics is of great significance. Many scholars have established creep constitutive models through empirical formulas and element combination models, and found that rock creep has significant nonlinear characteristics, and the accelerated creep stage is the most obvious. However, traditional constitutive models such as Nishihara model and Burgers model cannot reflect the nonlinearity of rock creep because of the constant parameters of the combined elements. [0003] In...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/28
CPCG01N3/28G01N2203/0025G01N2203/0071
Inventor 林杭张星雍睿曹日红汪亦显杜时贵
Owner CENT SOUTH UNIV
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