Analysis of fracturing characteristics of unconfined rock plate under edge-on impact loading.

The objective of this study is to investigate the fracturing characteristics of granite under impact loading. Generation and propagation of cracks from the specimen edge subjected directly to impact loading were captured by the ultrahigh-speed photography. Testing results indicate the existence of a critical impact velocity. At an impact velocity lower than the critical impact velocity, a damage zone will be generated on the edge subjected directly to impact and the damage zone area is varied, depending on the magnitude of impact velocity. At an impact velocity greater than the critical impact velocity, radial cracks appear on the boundary of the damage zone and propagate deep into the rock plate with further increasing impact velocity. The increases in radial crack length and damage zone area are affected by impact velocity and impact angle. However, at some impact velocity, damage zone area decreases while radial crack length increases, demonstrating the existence of an incubation period of crack forming. Comparison between testing and numerical results shows that at a constant impact velocity the fractured zone area and the crater depth are varied, depending on impact angle. The results are helpful to understand the fracturing process in rock subjected to impact loading. [ABSTRACT FROM AUTHOR]