Non-stationary and nonlinear visco-elastic shear creep model for shale

Yang, Sheng‐Qi; Cheng, Long

doi:10.1016/j.ijrmms.2011.06.007

Cited by 69 publications

(27 citation statements)

References 16 publications

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“…The nonlinear least square method (NLSM) (Zhu et al 2008;Yang et al 2011) is used to identify the model parameters of rocks. The square of the correlation coefficient R 2 is selected as the criterion to evaluate the accuracy of the model parameters.…”

Section: Nonlinear Damage Modelmentioning

confidence: 99%

Stress relaxation behavior of silty mudstone considering the effect of confining pressure

Zhang

Liu

et al. 2016

Environ Earth Sci

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Stress relaxation tests under confining pressures of 1 and 5 MPa were performed on saturated silty mudstone obtained from Badong Formation strata in the Three Gorges Reservoir area of China. The effects of confining pressure on the relaxation stage, magnitude, degree, time and average relaxation rate of rocks were analyzed quantitatively according to these tests. The results show the relaxation stage of rocks without change, the relaxation magnitude and average relaxation rate of rocks increase and the relaxation degree and time of rocks decrease as the confining pressure increases. Then, a damage variable was proposed to consider the weakening of rock parameters. A new nonlinear damage model was established by introducing the damage variable into the Hooke-Kelvin model. The Levenberg-Marquardt algorithm was adopted to identify the model parameters of rocks. Based on the identification results, the influence of confining pressure on the viscosity of rocks is the largest, followed by the viscoelasticity; also, that on the instantaneous elasticity of rocks is the smallest. Increase in confining pressure can effectively decrease the damage degree of rocks induced by stress relaxation. Therefore, the confining pressure has significant influences on the stress relaxation behavior of silty mudstone, which should not be ignored in design and construction of major projects.

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Section: Nonlinear Damage Modelmentioning

confidence: 99%

Stress relaxation behavior of silty mudstone considering the effect of confining pressure

Zhang

Liu

et al. 2016

Environ Earth Sci

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“…3. Parameters of every empirical function are obtained by the nonlinear least square method (NLSF) using the Origin Software (Yang and Cheng, 2011). Two statistical parameters: (a) the square of the correlation coefficient, R 2 , and (b) the reduced Chi square value, C 2 , are used to judge the goodness-of-fit of the fitted curves on the creep test data.…”

Section: Selection Of Four Functionsmentioning

confidence: 99%

“…Shengqi and Yuzhou (2010) reported observed creep behavior of sandstone under standard triaxial compression loading. Yang and Cheng (2011) studied the creep behavior under shear loading. They found the estimated shear creep parameters to vary with time.…”

Section: Introductionmentioning

confidence: 99%

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Creep Behavior Modeling of a Marble Under Uniaxial Compression

Chen

Kulatilake

2015

Geotech Geol Eng

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Axial strain-time curves for a marble sample were obtained by performing uniaxial compression tests with step loading. Axial strain rate-time data points were then obtained from the axial straintime curves. One power function and one exponential function were selected from the literature to fit the experimental creep data. Based on the characteristics of the plotted axial strain rate-time data points, one power function and one exponential function were proposed as possible functions to model the creep data. By comparing the goodness-of-fit of the aforementioned four functions through regression analysis, it was found that the two exponential functions fit the experimental creep data better than the two power functions. The two exponential functions showed very close goodness-of-fit levels on the experimental data. The proposed exponential function has only two parameters compared to that of the exponential function in the literature which has four parameters. Therefore, the proposed exponential function is selected as the creep model of marble. This model is also related to a built-up combined spring-dashpot model known as the generalized Kelvin model. The model parameter values of the generalized Kelvin model are then calculated by the parameter relations that exist between the generalized Kelvin model and the proposed exponential function.

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“…Rahimi and Hosseini (2014) conducted triaxial creep tests on thick-walled hollow cylindrical rock salt specimens, and developed a mathematical equation to estimate the strain rate in various stress fields. Yang and Cheng (2011) constructed a nonlinear viscoelastic shear creep model based on the H-K model by introducing a time index and found that this model allows for better prediction of the long-term deformation behavior of shale. Moghadama et al (2013) utilized an elasto-viscoplastic constitutive model to describe dilatancy, short-term failure as well as long-term failure during the transient and steady state creep of rock salt.…”

Section: Introductionmentioning

confidence: 99%

A creep constitutive model with variable parameters for thenardite

et al. 2016

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Results from the triaxial creep tests indicate that the relationship between steady creep rate of thenardite and deviatoric stress can be described with the Heard model. By combining the Kelvin model which reflects the primary creep property of rock with the Heard steady creep model, a Kelvin-Heard (K-H) creep model is constructed. However, the predicted curves from the K-H model are not in good agreement with the creep test data of thenardite. To improve the prediction precision, it is assumed that the viscosity coefficient of thenardite increases over time in primary creep stage, and an improved K-H model is proposed. Compared with the K-H model, the improved K-H model can more precisely describe the creep behavior of thenardite under a certain stress state. However, each of its parameters G, g ? , a and b has different values under different deviatoric stress levels. These four parameters all decrease with the increase in deviatoric stress, which is considered to establish an improved K-H model with variable parameters for thenardite finally. Comparison with the test data shows that this model can precisely predict the creep behavior of thenardite when 25 MPa B r 1 -r 3 B 40 MPa.

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Non-stationary and nonlinear visco-elastic shear creep model for shale

Cited by 69 publications

References 16 publications

Stress relaxation behavior of silty mudstone considering the effect of confining pressure

Stress relaxation behavior of silty mudstone considering the effect of confining pressure

Creep Behavior Modeling of a Marble Under Uniaxial Compression

A creep constitutive model with variable parameters for thenardite

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