Perimeter blasting in a 130 m road cut in gneiss with holes with radial bottom slots

This paper presents field trials with a new blasting technique. It uses a simultaneous firing of perimeter holes that have radial bottom slots instead of subdrilling and a bottom charge. The new technique has been tested in multiple row blasting in a 130 m long road cut in gneiss where it has been compared with ordinary smooth blasting. Extensive monitoring of drilling and drilling accuracy, slotting, rock wall properties and the remaining half-casts has been made. The blast damage in the wall was detected by a diamond sawing and dye penetrant technique.