Dynamic Strength of rock under High strain rates

In rocks, brittle deformation depends on loading rating. With increasing rates, usually greater than ~10² s^-1 rock strength increases significantly that results intense fragmentation. Dynamic conditions necessary for rate dependent brittle failure can occur during impact events, seismic ruptures and landslides. Among the geoscientist and rock engineers, Split Hopkinson Pressure Bar (SHPB) is often used for the study of dynamic behavior of rocks under high strain rate condition. Present study focuses on strength behavior of sandstone over the range of strain rate (3.6×10^-5 - 2.4×10² s^-1) using compression testing machine and Split Hopkinson Pressure Bar (SHPB). The failure mode is also captured by high speed camera. The result demonstrates that dynamic compressive strength increases with increasing strain rate and follows Kimberley’s universal theoretical scaling relationship. Dynamic increase factor (DIF) also shows strong dependency on strain rate. The degree of fragmentation is also compared with existing theoretical fragmentation models. The average fragments size shows strong strain rate dependency over the entire testing range. With the increasing strain rate more pulverized state were observed after the failed specimens. Moreover, the mean fragment sizes are well described by power law function of strain rate.