Geological control over blast fragmentation

CIM Bulletin, Vol. 87, No. 983, 1994

Yves C. Lizotte, Department of Natural Resources Canada, CANMET, Mining Research Laboratories, Experimental Mine, Val d'Or, Quebec, and Malcolm J. Scobie, Department of Mining and Metallurgical Engineering, McGill University, Montreal, Quebec

Blast fragmentation is affected by the physical and mechanical characteristics of the rockmass as determined by geology as well as the explosive energy, the partition of this energy, the actual amount of energy transmitted to the rockmass, the blast geometry and the detonation sequence. This paper reviews studies of the influence of geology on blast fragmentation, particularly structure, i.e. the in situ or inherent fragmentation arising from rock discontinuities. Prior structural studies have mainly been limited to comparing equivalent diameters of the in situ blocks with the size distributions of the blasted material. No criteria exist to integrate structure into blast design. This paper reviews on-going studies of the blasted fragment shape and size observed in different rock masses aimed at analyzing geological control over blasting. Digital photoanalysis was applied to measure size and shape distributions, to correlate results with block size distributions and shape parameters of the inherent fragmentation. An integrated and comprehensive fragmentation assessment procedure which accounts for geological control is proposed. The potential of this research is to provide a greater understanding of the true contribution of explosives to fragmentation, the effects of fragment shape on system productivity and the reduction of blast-induced damage.

Keywords: Blast fragmentation, Fragmentation, Geological controls.