Testing Method On Dynamic Fracture Toughness Of Rock

Based on Split Hopkinson Pressure Bar (SHPB) testing system, and using Flattened Cracked Chevron Notched Brazilian Disc (CCNBD) specimen, this paper researches the dynamic fracture toughness test method of the same basalt with three different depths. It can extend the quasi-static fracture toughness testing equation into dynamic fracture toughness method, only if the dynamic force balance was satisfied. And it has proposed a dynamic failure criterion to determine the critical value of the stress intensity factor, i.e. the minimum dimensionless stress intensity factor and the maximum stress corresponded. The LS-DYNA program has been adopted to analyze the energy release of the testing system, and verified the two fundamental assumptions (one dimension stress wave and stress equalization). It has obtained that the dynamic fracture toughness increases with the loading rate, and illuminated it from the point of multi-axial stress field at the crack tip. It has discussed the influence factor of the fracture toughness, combined with rock static tensile strength. It provides estimation of rock failure from the micro crack growth, propagation and coalescence induced by tensile strength.