The effect of aspect ratio of rock samples on the dynamic characteristics of rocks under shock loads

Abstract

The dynamic behavior and characteristics of rocks under various dynamic conditions such as blasting, excavation and failure of rock engineering structures, the rupture of the earth crust during earthquakes have been receiving great attention in recent years. As a result, there are various studies for developing appropriate experimental techniques to understand and evaluate dynamic mechanical behavior and characteristics of rock. Split Hopkinson Pressure Bar (SHPB) experimental technique is utilized for evaluating the strength of rocks under high strain rates. The aspect ratio of rock samples used in this technique does not satisfy the conventional aspect ratio utilized in static tests and it is generally less than 1.0. It is well known that if the aspect ratio is less than 2, the failure process will be greatly influenced by the platens at the ends of samples. The authors investigated the effect of the aspect ratio on the overall behavior of rocks under shock loads using their own shock test device. Various rocks used for this purpose, including frictionless artificial material such as paraffin. The experimental results so far clearly showed that the aspect ratio is of great importance and it cast some doubts on experimental findings from the SHPB tests. The authors discuss the experimental results and discuss the effect of the aspect ratio on dynamic characteristics of rocks in this study.