Study on the characteristics of blast-induced damage zone by using the wave velocity field inversion technique

The rock excavation by drilling and blasting method would lead to damage around the blasting hole, which could significantly affect the long-term stability of surrounding rock mass in tunnel, slope, or bedrock. To qualify the characteristics of blast-induced damage zone, we proposed a wave velocity field inversion imaging method, which combines multistencils fast marching methods and simultaneous iterative reconstructive technique to quickly inverse and quantify the blast-induced cracked zone surrounding the borehole. The finite-discrete element method, which has advantages in simulating the fracture and fragmentation of rocks, was used to simulate the blasting process and acoustic wave testing. The ground vibrations induced by the blasting were monitored simultaneously and the acoustic waveforms are used to invert the wave velocity field before and after blasts. The inverted wave velocity field is compared with the blast-induced cracked zone, and the relationship between the radius of the crushed zone and the cracked zone under different charges was studied. It is found that the ratio of the crushed zone radius and the cracked zone radius decreases with the increasing charge. Moreover, the relationship between the peak particle velocity at 30 m away from the borehole (PPV₃₀) and the distribution of the cracked zone was determined.