Understanding Impact Loading on Rocks and Its Implication: An Insight

Many of the applications in rock engineering require high-strain rate dynamic mechanical properties in the order of 100–1000/s, feasible to study using split-Hopkinson pressure bar (SHPB) apparatus. Unlike ductile materials like metals, < 1% is often the failure strain of brittle materials. Additionally, in many rock engineering applications, multi-axial loading is expected. Although SHPB is common equipment modified for material testing, certain fundamental concerns should be carefully considered when applied to rock specimens. Many literatures are available conducting dynamic impact tests on rocks using SHPB, performed using small diameter rods. Moreover, the multi-axial confining loading is highly relevant to underground rock engineering problems. In this presentation, preliminary work of high-strain dynamic testing on rocks is done using SHPB. A preliminary review of the impact of loading on rocks and related applications is also presented. Few preliminary test results with SHPB on rocks are also presented. A brief insight into the customization requirement, issues and challenges, and corresponding limitations with the SHPB is discussed. Experiments on artificial rock specimens (using gypsum plaster) under high-strain dynamic loading are carried out, and the corresponding results from preliminary experiments with rock-like material specimens are discussed.