Time-dependent damage constitutive model for the marble in the Jinping II hydropower station in China

To accurately describe the damage creep properties of marble, especially during the acceleration creep phase, creep testing was performed on the marble in the Jinping II hydropower station in China. Based on the experimental results, a time-dependent damage constitutive model was proposed in terms of fractional calculus theory and damage variables to describe these time-dependent damage characteristics. The time-dependent constitutive equations were derived for constant loading levels below and above the marble's long-term strength. The robustness and parameter sensitivity of the proposed model were analysed by utilizing data of creep testing. The results of the analysis showed that the proposed model could describe not only the attenuation and steady-state creep of marble but also the acceleration creep characteristics and negative exponential attenuation law of the yield strength over time when the constant loading was above the long-term strength. These are crucial to failure prevention during rock engineering construction and operating periods.