Dynamics fracture characteristics of cylindrically-bored granodiorite rocks under different hole size and initial stress state

Abstract

A modified Split Hopkinson pressure bar (SHPB) was used to carry out dynamic and static combined loading on prefabricated granite samples. Meanwhile, digital image correlation (DIC) technology was used to evaluate the failure mode of samples with different cylinder hole sizes under different loading conditions. In addition, the dynamic failure characteristics of different circular tunnel radii were obtained by numerical simulation software under impact loads. The influence of different normalized times and Poisson’s ratio on the dynamic stress concentration factor (DSCF) distribution around the circular cavity was obtained theoretically. The experimental results show that with the increase in hole diameter and pre-stress, the hole edge damage changes from tensile damage to compression. Numerical simulation reveals the influence of 3D initial stress on the failure of a tunnel, the results showed that the initial stress promoted the compression shear failure and the increment of initial stress would restrain the tensile crack around the tunnel. Furthermore, a theoretical solution indicated that with the increase of Poisson’s ratio, the tensile stress on the 0 and π direction increases; with the increase in normalized time, the tensile stress on the incident side decreases first, followed by an increase. When the normalized time increases to 6 ms or higher, the value of the DSCF on the tunnel rarely changes and the value of the DSCF at this time is close to the distribution of steady-state incidence.