Dynamic mechanical response and failure behaviour of single-flawed rocks under combined compression-shear loading

Abstract

In deep underground engineering projects, flawed rocks are often subjected to dynamic compression-shear loading owing to the arbitrary distribution of structural planes in rock mass. Understanding the dynamic mechanical response of flawed rocks under compression-shear loading is of great significance for rock engineering construction. In this study, the mechanical response and failure behaviors of flawed rock specimens subjected to dynamic compression-shear loading are studied by introducing an oblique cubic flawed specimen into the split Hopkinson pressure bar (SHPB) tests. Firstly, the stress distribution of the oblique flawed specimen is analyzed by using the finite element method. Numerical results show that the stress concentration zones are distributed along the short diagonal of oblique rock specimens, which validates the oblique specimen is an effective method to investigate the dynamic compression-shear failure behaviors of flawed rocks. Then, dynamic impact tests are conducted on oblique flawed rocks with different configurations. The experimental results indicate that the oblique angle, the flaw inclination angle, and the strain rate significantly affect the dynamic strength and deformation characteristics of the rock. Utilizing high-speed digital image correlation (DIC), the progressive cracking behavior and failure modes of flawed rocks under dynamic compression-shear loading are analyzed. The mixed compression-shear cracking dominates the failure of flawed rock specimens. In addition, the energy dissipation density and fragmentation degree also exhibit a strong strain rate dependency, and they are positively correlated with the dynamic strength of the flawed rocks.