Scaling law of average failure rate and steady-state rate in rocks

Abstract

Abstract-The evolution properties in the steady stage of a rock specimen are reflective of the damage or weakening growth within and thus are used to determine whether an unstable transition occurs. In this paper, we report the experimental results for rock (granite and marble) specimens tested at room temperature and room humidity under three typical loading modes: quasi-static monotonic loading, brittle creep, and brittle creep relaxation. Deformed rock specimens in current experiments exhibit an apparent steady stage characterized by a nearly constant evolution rate, which dominates the lifetime of the rock specimens. The average failure rate presents a common power-law relationship with the evolution rate in the steady stage, although the exponent is different for different loading modes. The results indicate that a lower ratio of the slope of the secondary stage with respect to the average rate of the entire lifetime implies a more brittle failure.

Creep and permeability evolution behavior of red sandstone containing a single fissure under a confining pressure of 30 MPa

“…The evolution of the strain rate during the creep stage is essential to analyze the time-based deformation of rock. Hao et al 29,40 presented a detailed study and discussion about the creep rate and how to define the steady-state and provided a relationship between failure-time with steady-state creep rate. Considering that the magnitude of the creep rates under relative high deviatoric stresses was larger than those under low-stress levels, the creep rates were plotted in logarithmic coordinates.…”

A model for describing and predicting the creep strain of rocks from the primary to the tertiary stage

“…The time to failure decreases as the applied stress and steady-state rate increase. [14][15][16] During the primary and secondary creep stages, acoustic emissions (AE) took place through almost the whole sample, indicating the cracking or/and crack propagation during the two creep stages. These results can explain the occurrence of reversible and irreversible strains when the rocks were submitted to loading and unloading conditions.…”