Mechanics of rock breakage by blasting and its application in blasting design

The process of rock fragmentation involves both gaseous and shock wave energy action but the latter is more effective at smaller burdens. Fragmentation and toe problems were generally encountered in massive rocks for a burden height ratio greater than 0.3. These problems were not observed in closely jointed rocks even when the ratio was as high as 0.5. A ratio of less than 0.2 did not cause backbreak and may be applicable in smooth blasting operations to produce stable ultimate excavation face. Fragmentation and toe problems can be minimized by adopting a reduced burden (less than 0.3 times the bench height and a larger spacing (greater than 1.5 times the burden).