Dynamic response and failure mechanism of Brazilian disk specimens at high strain rate

The effect of strain rate on the failure mechanism of rocks is one of the most important aspects in the field of rock dynamics and has been considered in many research works due to its extensive application. This study focuses on dynamic features and failure mechanism of Brazilian disk specimens under high-rate loading. For this purpose, particle flow code 2-dimensional (PFC2D) was used for simulation of Brazilian disk samples. The numerical models were validated by comparing with results of uniaxial compression, Brazilian and Split-Hopkinson Pressure Bar (SHPB) laboratory tests and it is demonstrated that the result of numerical modeling has a good agreement with those of the experimental measurements. The validated numerical model was used for further study of the mechanical behavior of rock specimen at high strain rate. The results of numerical models revealed that there are three different of failure modes for Brazilian disk specimens at different strain rate: (1) tensile splitting failure mode for specimen at strain rate smaller than 150 (1/s), (2) branching failure mode when strain rate varies in range of 150-600 (1/s) and (3) crushing failure mode when the strain rate increases to more than 600 (1/s).