Effect of loading rates on mechanical behavior and strain localization characteristics of sandstone.

Determining the effect of loading rates on rock mechanical properties and deformation behavior is of vital importance for underground engineering with high-intensity excavation. In this study, uniaxial compression experiments with the digital image correlation technique were conducted to investigate the mechanical properties, failure modes, and apparent strain fields of the sandstone samples under different quasi-static loading rates. The loading rate effect on the characteristics of strain localization and energy was subsequently analyzed. Results show that with increasing loading rates, both the elastic modulus and uniaxial compressive strength increase logarithmically, and the failure mode changes from shear failure to tensile failure. Meanwhile, there are relationships between the initiation and development of strain localization and the loading rates. As the loading rate increases, the stress and stress level of strain localization initiation and the expansion rate of strain localization at most time increase gradually, while the duration from strain localization initiation to macro-failure decreases. The expansion area of strain localization has no obvious change pattern. In addition, the increase of loading rates enhances the energy absorption, storage, and dissipation properties of the samples, resulting in a higher energy state. It is the essential reason for the differences in mechanical behavior and strain localization of sandstone under different loading rates. [ABSTRACT FROM AUTHOR]