Blast vibration is essentially stress wave propagation in rock or structures in the vicinity of a blast. However, blast vibration has always been quantified in terms of peak particle velocities (PPV) or accelerations (PPA), and a meaningful relationship between blast vibration and strain/stress has not been established. The failure criteria for rock and structures in terms of stress are relatively well established. If the blast vibration can be described in terms of dynamic strain and stress states (tensors) at a monitoring location, the damage of blast vibrations can be evaluated against rock strength criteria, such as a tensile or a Mohr- Coulomb failure criterion, etc. In this way, the cumulative effect of blast vibration on rock structures and the vibration limit for a particular operation can be determined more objectively. This paper presents a method for estimating rock tri-axial dynamic strain and stress tensors from the measurement of near field blast vibration. A method to estimate the strain rate due to the dynamic loading from blast vibration is also established.
Blast vibrations are stress waves propagating in rock. However, blast vibration has always been quantified in terms of the peak particle velocity (PPV) and peak particle acceleration (PPA), but these parameters cannot be directly related to rock damage resulting from the vibration. A frequently asked question from the blasting community is “What is the safety factor for my site if we set the vibration limit to be 2 in/s (51 mm/s)?” If the blast vibrations could be described in terms of dynamic stress states (tensors) at a monitoring location, we might be able to estimate the blast damage or the effect of the blast vibration, since the failure criteria for rocks (in terms of stress) have been relatively well established.