Anisotropic Mechanical Behavior of Stratified Sandstone Subjected to Cyclic Loading

Abstract

To explore the influence of bedding structure on mechanical properties and failure mechanism of anisotropic rocks, six stratified sandstone specimens with different bedding orientations were tested by uniaxial static and cyclic loading. Acoustic emission (AE) and digital image correlation (DIC) were exploited to analyze the mechanism of crack initiation and propagation. The results show that with the increase of the bedding orientation, the peak strength of the stratified sandstone decreases first and then increases, behaving an obvious anisotropic characteristic. The AE characteristic-stress-strain curve can be divided into four stages: crack closure stage, linear elastic deformation stage, stable crack growth stage, and unstable crack growth stage. Moreover, as the bedding orientation increases from 30° to 90°, the crack closure stage gradually lengthens, while the linear elastic deformation stage first shortens and then lengthens. Under uniaxial static compression, due to the presence of bedding surface, the rock surface has a relative slip trend as a result of the uneven distribution of strain on the left and right parts, and the strain field boundary is almost consistent with the bedding orientation. Furthermore, cyclic loading can increase the rock stiffness, and the stain field boundary of 60° stratified sandstone sample in each cycle is slightly different in the cyclic loading.