Discussion on blasting vibration monitoring for rock damage control in rock slope excavation

Drill and blast is a commonly used method for rock slope excavation in hydropower engineering. During blasting excavation of rock slopes, far-field vibration monitoring on the first upper berm for statutory compliance is usually performed to control the blast-induced rock damage to the final slope face. In this study, for the rock slope excavation in the Jinping-I hydropower station, the field vibration monitoring and acoustic testing are presented to investigate the vibration characteristics on the first upper berm and the damage depth in the current bench. The relationship between the PPV on the first upper berm and the PPV damage threshold on the damage zone boundary is also studied through three-dimensional FEM simulations. The results show that on the first upper berm, the maximum vibration velocity component occurs in the vertical direction. While on the blasting damage zone boundary, the horizontal radial vibration velocity is the maximum component. For the Jinping-I slope with a bench height of 30 m, the radial PPV on the inner side of the first upper berm is 2.06% of the PPV threshold on the damage zone boundary. This ratio is increased as the bench height decreases. Therefore, the bench height of the rock slope is an important factor that cannot be ignored in determining the allowable vibration velocity for rock damage control.