Energy evolution and deformation features of re-loading creep failure in yellow sandstone after cyclic water intrusion

To assess the long-term stability of rock bodies after excavation or slope excavation under external forces, uniaxial compression, and graded loading and unloading creep tests were performed on variable-saturation yellow sandstone after cyclic water intrusion. The energy evolution and deformation mechanisms of rocks during loading, creep, unloading, and holding were analyzed. Furthermore, the reloading creep behavior of variable-saturation rocks under cyclic water intrusion was investigated. Finally, a novel model is developed to describe this deformation using principles from damage mechanics and the viscoelastic-plastic theory. The following results were obtained: (1) Instantaneous deformation demonstrated a positive correlation with creep stress levels. The phenomenon of creep deformation exhibited nonlinear growth as the stress increased. (2) The nonlinear change rule of the plastic strain energy and dissipated energy of the rock under the action of a creep load could be characterized by a quadratic polynomial and power function, respectively, in accordance with an increase in the strain difference. (3) By analyzing the evolution of all levels of loading and unloading section energy and introducing an energy attenuation coefficient (K_i) based on the law of change in the graded loading and unloading creep test, an accurate destructive stress prediction was obtained. (4) A nonlinear creep damage constitutive model was constructed by combining the method of unsteady linear element and damage treatment. The accuracy of this model was assessed through model identification, validation, and evaluation of the prediction deviations from the test curves using experimental data. The findings of this study are of great significance for the prevention and control of creeping landslides initiated by water-related steep rocky slopes undergoing cyclic water intrusion.