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This study develops a unified micromechanical induced anisotropic model to predict the instantaneous and longterm behaviors of rock materials under cyclic loading. By integrating a thermodynamic framework with the Mori–Tanaka homogenization method, the model captures the anisotropic damage evolution considering nonuniform microcrack growth. The model incorporates the interaction between microcrack-induced damage and frictional effects, enabling a more accurate prediction of nonlinear behaviors. A fatigue damage variable is introduced to represent the progressive degradation. The plastic deformation is attributed to frictional sliding along oriented microcracks, while instantaneous and fatigue damage evolution are driven by crack growth and subcritical cracking, respectively. The model is validated against experimental data for varying rock types, demonstrating its ability to reproduce key mechanical behaviors, including nonlinear mechanical response, fatigue life, and nonuniform damage evolution. The proposed model provides a robust and comprehensive framework for analyzing the longterm behavior under cyclic loadings.
Zhang et al. (Sun,) studied this question.