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Development of a Method for Blasthole Pattern Design in Surface Mines

Author:
[ H. Moomivand ] - Assistant Professor of Mining Engineering, Mining Engineering Department, Faculty of Engineering, University of Urmia

Abstract:

A comprehensive investigation was done on optimizing powder factor and ratio of burden (B) to blasthole diameter B/fi(h) by doing several stages of drilling and blasting practically in different mines. Optimization was investigated to minimize the cost of the rock fragmentation process including drilling and blasting, secondary blasting, removing the large boulder (oversize rock) until the optimized fragmentation, powder factor and B/fi(h) ratio were achieved. Rock mass is not a homogeneous, isotropic and continuous solid material and it contains various discontinuities. The complicated in situ factors control rock fragmentation by blasting, as development of an adequate method for design of drilling and blasting had been a difficult task. Rock mass parameters affecting the powder factor and B/fi(h) ratio were investigated extensively in different mines and discontinuity plane aperture of rock mass as a new parameter affecting the powder factor and B/fi(h) ratio was also applied. Parameters affecting the rock mass fragmentation were summarized to be discontinuity plane aperture, discontinuity plane spacing, discontinuity plane orientation, rock mass description and unconfined compressive strength of rock material. The quantitative effect of each parameter on B/fi(h) ratio was indicated by a number (rating). The total values of numbers were named “Rock Fragmentation Index” (RFI). The numbers were arranged in a way that RFI was equal to B/fi(h) ratio. Parameters of RFI and their rating were proposed in a table to use as a new simple method of blasthole pattern design.

Keywords:

Drilling, Blasting, powder factor, Rock fragmentation index, Discontinuities