Shear failure behavior and damage evolution mechanism of sandstone under pre-static loading and low-frequency dynamic disturbance

To investigate shear failure behaviour under disturbance loads, shear tests on sandstone were conducted using low-frequency disturbance loads, combined with acoustic emission (AE) and digital image correlation (DIC) technology. The shear mechanical properties were investigated under varying pre-static load levels and disturbance amplitudes. The results indicated that the crack initiation stress, crack damage stress, and peak stress in sandstone shear decreased as the disturbance load amplitude increased. The impact of the disturbance load on the crack initiation and damage stresses are positively and negatively correlated with the pre-static load level, respectively. Disturbance loading causes a linear decrease in cohesion and a slight increase in the internal friction angle, which together lead to a reduction in shear strength. This highlights the dominant role of cohesion degradation in the mechanical weakening of sandstone under dynamic-static coupled conditions. Shear cracks dominate under constant and disturbance loadings exceeding 70 %. Disturbance loads induced more shear cracks. The b-value increased with the disturbance amplitude, and high-amplitude disturbances promoted small-scale microcracking in sandstone. An increased disturbance amplitude weakened the ability of the specimen to store elastic energy and bearing capacity, whereas an increased pre-static load level enhanced these abilities. We offer insights into the stability analysis of rock masses under dynamic normal low-frequency disturbance.