Vibration monitoring and blast damage assessment in underground metal mines

With the introduction of large diameter deep hole blasting in underground metal mines in India for extraction of ores, there was a serious concern for safety and stability of underground structures. This paper deals with vibration monitoring and damage assessment in five different metal mines. The damage was assessed by visual observation and the rock mass conditions were evaluated through RMR values. Attempts were made to correlate the extent of damage with peak particle velocity (PPV). Using the data generated, a generalised predictor equation was derived for prediction of ground vibration in other mines. The analysis of the field data indicates that vibrations produced by large and small blasts in a mine can be grouped ' together to derive a predictor equation for the same mine. The degree of damage to the rock mass vis-a-vis supports requirement depends on the intensity of ground vibration and rock mass quality. In general, falling of loose pieces' is expected at PPV greater than 200 mm/s and formation of new cracks' at PPV exceeding 300 mm/s.