Experimental study of the dynamic characteristics of sandstone with preexisting creep damage

Damage generated from creep deformation is pervasive in rock, which is assumed to influence the mechanical performance of rock. However, the influence of creep damage on the dynamic characteristics of rock has not been well understood. Here, a rock creep-impact test apparatus is used to investigate the preexisting creep damage on the dynamic performance of sandstone. The results demonstrate that a higher creep stress results in more initial microcracks in sandstone, leading to a higher damage-cumulation rate. The impact number is more sensitive to the creep-stress level than the creep duration. During the dynamic impact, a higher creep stress leads to a larger peak axial strain and a larger residual axial strain, whereas a sandstone sample tends to dilate with increasing constant stress and load duration. Moreover, the larger the constant stress level and creep duration, the smaller the proportion of the second stage of damage of sandstone under impact loading. These results are helpful to the understanding of the damage and failure process of deep rock structure exposed to dynamic loading.