Effect of Loading Rate on Fracture Behaviour of Rock Materials

In this paper, experiments are carried out to study the quasi-static and dynamic fracture behaviour of sedimentary, igneous and metamorphic rocks. The notched semi-circular bending method has been employed to determine fracture parameters over a wide range of loading rates using both a servo-hydraulic machine and a split Hopkinson pressure bar (SHPB). The time to fracture, crack speed and velocity of the moving specimen halves are measured by strain gauge, crack propagation gauge and high-speed photography on the macroscopic level. This study reveals clearly that: dynamic crack initiation and growth toughness increase with the increase of loading rate and crack speed; the kinetic energy of the moving specimen halves increases with increasing impact speed of the striker; and dynamic fracture energy and increases rapidly with increasing crack speed.