investigations on impact of Blasting in tunnels

Blasting with longer advance per round leaves an impact both visible (in the form of overbreak) and invisible (cracks) in the surrounding rockmass, however, a number of controlled-blasting techniques, that is line drilling, pre-splitting, and smooth blasting, have been developed to minimise this problem. These techniques require additional drilling, controlled charging, and detonation, and thus, are not preferred in regular development activities. Investigations have been carried out in five different horizontal development drivages of metal mines to assess the blasting impact using burn cut and arrive at the blast-induced rock damage (BIRD) model. Vibration monitoring close to the blast was carried out using accelerometers for the first time in India to develop vibration predictors and overbreak threshold levels for individual sites. This paper reports the development of the overbreak predictive model (BIRD) for burn cut blasting in hard rock drivages by combining the relevant rock, blast design, and explosive parameters. A multivariate statistical model has been developed and validated and the same can find ready application in tunnels and mines for exercising suitable engineering controls both in blast design and explosive selection for reduced basting impacts.