Abstract: It is significant to reveal the evolution characteristics of rock deformation field at various loading rates for safe construction and disaster warning in rock engineering. In this study, uniaxial compressive experiments were conducted on red sandstone at four different loading rates (0.01, 0.05, 0.1 and 0.5 mm/min), and then the evolution of deformation field was analyzed by the digital speckle correlation method. Furthermore, the relationships between the loading rate and rock deformation localization, energy accumulation and release and Poisson's ratio were studied, respectively. The results show that the peak strength and the brittleness of rock increases with the increase of loading rate. It is found that with the higher loading rate, the starting position of rock deformation localization is closer to the value of peak strength. Moreover, the corresponding stress value in this position increases generally. The Poisson's ratios of rock specimen are obvious different at various loading rates. The overall trend is that with increasing loading rate, the Poisson's ratio decreases before the deformation localization, while it increases during the stage of deformation localization. With the increase of loading rate, the density of rock deformation energy increases at the energy accumulation stage, and the energy release rate increases in the process of energy release.

Key words: loading rate, deformation localization, digital speckle correlation method, Poisson's ratio, energy evolution