A transition index for rock failure due to liquid impact

Impingement of rocks by liquid projectiles causes the erosion of structures, but is also the principal process for non-traditional drilling and cutting methods, such as hydrodemolition, hydrodynamic fragmentation, and cavitating drilling. Based on loading and failure analyses, an elastic–plastic transition condition is proposed which is characterised by a toughness-strength-index, KIc2/(σC3cM); here KIc is the fracture toughness, σc is the compressive strength, and cM is the speed of sound in the material. Materials with low values (granite, quartz, feldspar) respond elastic, whereas materials with high values (limestone, schist) respond elastic–plastic. Experiments are performed to investigate the response of four rock materials in order to verify the proposed transition-index.