STUDY OF SMOOTH BLASTING EFFECTS ON TUNNELLING IN JOINTED HARD ROCK.

In this study, the applicability of smooth blasting for tunneling in jointed hard rock was discussed with reference to the field measurements. In the field test, spacing, burden and specific charge were varied into three levels individually, and 27 cases of smooth blasting tests were carried out. The test results were evaluated according to the over-break and under-break and the drill hole contour ratio. The field test results showed that the variations of spacing and burden have little effect on the smooth blasting results, but a smaller specific charge gives a little better result than a larger one. The tests also showed that the joint structure has a great influence on the blasting results.