Abstract
In this study, the smoothblasting in hard granite tunnel was discussed with reference to the results of three field tests which aimed at the minimization of overbreak and underbreak. In the tests, the drilling was practiced by the aid of automatic drilling machine. Among many factors which effect on the smooth biasting result, particular attention was payed to the drilling precision. Differences between the designed and actual blasted faces were statistically analized and smooth blasting results were discussed from its point of view.
The study revealed that not only the blasting techniques but also the drilling precision give a great effect on the smooth blasting result in hard granite tunnels.
