Nonlinear creep properties and time-to-failure prediction of sandstone under saturated and dry conditions

The moisture content of rock significantly influences its time-dependent deformation behavior. This paper studied the creep behavior of sandstone under saturated and dry conditions under different driving stress ratio (not the same creep stress level).Their impacts on the time-to-failure (TTF) of sandstone were also investigated. The results show that under an identical driving stress ratio, the dry specimens' creep strain and steady-state creep rate are relatively higher than those of the saturated ones. Nevertheless, the water-saturated specimen has a shorter creep strain path and TTF due to the softening effect of water. It is evident that in terms of creep deformation and creep rate, the impact of creep stress is much more significant than that of moisture content; however, in terms of creep TTF, the moisture content of sandstone plays a dominant role. The rationality of the generalized Kelvin, Burgers, and power-law creep models were evaluated based on the experimental data. The power-law model was found to be capable of fitting the test data, and better predicting sandstone creep deformation than other two models. Finally, based on the assumption of a critical strain value εcri, a method for predicting creep TTF from limited laboratory data was proposed, providing a foundation for incorporating TTF prediction into continuum numerical simulations.