Abstract
Rocks may exhibit time-dependent behaviors. Long-term strength criterion significantly dominates creep failure of rocks. Rocks contain many microcracks, which lead to degrade of long-term strength. In this paper, it is assumed that there exist three-dimensional penny-shaped microcracks in rocks. The mode II stress intensity factors at tips of three-dimensional penny-shaped microcracks in Burgers viscoelastic rock matrix is derived. A novel micromechanics-based three-dimensional long-term strength criterion is established to consider the effects of time and the intermediate principal stress on creep failure of rocks. By comparison with the previous experimental data, it is found that the novel micromechanics-based three-dimensional long-term strength criterion is in good agreement with the experimental data.
Highlights
I n the past several decades or more, extensive laboratory creep experiments were conducted to study the creep behaviors of many kinds of rocks [1,2,3,4,5]
A novel micromechanics–based three-dimensional nonlinear long-term strength criterion is established to study the effects of time and the intermediate principal stress on the creep failure of rocks
By comparison with experimental data, it is found that the novel micromechanics–based threedimensional long-term strength criterion is in good agreement with the experimental data
Summary
I n the past several decades or more, extensive laboratory creep experiments were conducted to study the creep behaviors of many kinds of rocks [1,2,3,4,5]. A novel micromechanics–based three-dimensional nonlinear long-term strength criterion is established to study the effects of time and the intermediate principal stress on the creep failure of rocks. 3 / 2 in the maximum-stress criterion [19], t0 is the time of creep failure of microcracks, KIC is toughness of rocks, which can be obtained by induced tensile strength and crack length, namely. The creep failure characteristic parameters should satisfy the following three principles: firstly, the expression of the creep failure characteristic parameter should be in a simple mathematic one; secondly, the higher the minimum principal stress, the lower the micro-failure orientation angle; the theoretical result should agree well with the experimental data. According to the second principle and Eq (21), the cosine of the micro-failure orientation angle can be expressed in following form: cos =. Where cos is defined as the rate of change of cos to the maximum principal stress. 1
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