Laboratory and numerical investigation of anisotropic creep behavior of transversely isotropic composite rock

The structural anisotropy has obvious effect on the time-dependent behavior of composite rock. A series of creep tests and numerical simulations were carried out to investigate the anisotropic creep behavior of composite rock. The creep tests were conducted on Three-Dimension Printing (3DP) composite rock-like samples with varying inclination angles to mitigate the effects of the high variability inherent in natural composite rocks. The test results revealed that, due to the influence of structural anisotropy of the 3DP composite rock, their steady creep rate demonstrates a clear inverse U-shaped variation as the inclination angle increases from \(0^\circ \) $0^{\circ }$ to \(90^\circ \) ${90}^{\circ }$ . Additionally, the variation of the steady creep rate increases with increasing creep stresses. Based on the creep tests, numerical models of composite rock were established to further investigate the anisotropic creep behavior of composite rock. The numerical analysis showed that the inverse U-shaped variations of the steady creep rate fluctuate with increasing of the sample size until a stable value is reached. And the anisotropic creep behavior of composite rock is dependent on the volumetric proportion of the soft layer in the composite rock, and is little affected by the thickness of the soft layer, provided that the proportion of the soft layer remains constant.