A Method to Identify Blasting-Induced Damage Zones in Rock Masses Based on the P-Wave Rise Time

Abstract

Abstract Blasting-induced damage zones in rock masses are commonly identified by changes in the ratio of the P-wave velocities before and after blast. In ultrasonic tests, water is usually adopted as the coupling medium. As the ultrasonic wave propagates in the aqueous medium, the measured P-wave velocity will be affected by the water coupling distance between the transducer and the wall of the test hole. However, compared to the rock material, due to the lower dispersivity of the aqueous medium, the P-wave rise time is nearly unaffected by water coupling distance. The method based on P-wave rise time is as simple and feasible as the method based on P-wave velocity while employed in field testing. Furthermore, when P-wave rise time is used to detect blasting-induced damage zones, the measured data are in less variability and greater reliability than that acquired from the method based on P-wave velocity. As a result, while the P-wave velocity data are highly variable, the damage zone is difficult to discriminate, but it can be relatively easily discriminated using the P-wave rise time.