Experimental study on strain localization and slow deformation evolution in small-scale specimens

Abstract A kind of slow deformation wave is produced in the crust under the action of internal and external factors, which plays an important role in the formation and occurrence of earthquakes. In this paper, uniaxial compression tests are carried out on red sandstone samples with uniform texture. Displacement controlled loading methods are adopted, and the loading rates are 0.1 mm/min, 0.5 mm/min and 1.0 mm/min, respectively. The micro-characterization method of speckle photography and DIC processing technology are adopted. The transfer characteristics of slow deformation and strain localization of red sandstone specimens during loading and deformation are discussed. The results show that the boundary advance velocity is proportional to the slow deformation transfer velocity with the change of position, so it can be considered that the slow deformation transfer velocity is equal to the particle motion transfer velocity. The formation and development of sample strain localization may be determined by the flow channel, nucleation and Luders zone evolution. The formation of the Luders band is related to the maximum value of the flow channel, and as deformation increases, the Luders band merges and develops with the maximum value of the nearby flow channel. By applying different loading rates, the influence of loading rate on the average transfer velocity of slow deformation was obtained; the slow deformation wave during seismic migration has similar characteristics to the deformation transfer in the experiment, therefore the research results have reference significance for further studies on the evolution characteristics of slow deformation waves and seismic migration.