Mechanical properties and failure characteristics of anisotropic shale with circular hole under combined dynamic and static loading

Abstract

In deep hard rock mines, the drilling and blasting method is mainly used for mining, which results in a complex environment of high static stress and frequent dynamic disturbance in some underground engineering surrounding rocks for a long time. In addition, a large number of underground engineering are in the geological tectonic zone with poor stability, which often triggers rock disasters when stress waves propagate to the bedding. Therefore, it is significant to study the failure process and mechanism of underground engineering in bedded rock masses under combined dynamic and static loading. In this study, a combined dynamic and static impact experiment was conducted on circular-hole-containing shale specimens with different bedding angles using a modified split Hopkinson pressure bar (SHPB) device, and the damage process was recorded using Digital Image Correlation (DIC) technique. The experimental results show that the stress-strain curves of shale specimens under combined dynamic and static conditions include three stages elasticity, yielding, and failure. With the increase of the bedding angle, the dynamic strength and Young's modulus of the specimens showed a trend of decreasing and then increasing, with obvious anisotropy. However, with the increase of pre-static load, the dynamic strength and Young's modulus of the specimens showed a tendency to increase first and then decrease. In addition, repeated refraction (transmission) and reflection of the stress wave between the beddings and the stress concentration phenomenon of the circular holes resulted in different failure characteristics of the specimens with different bedding angles.