Abstract
Pillar stability is an important factor for safe working and from an economic standpoint in underground mines. This paper discusses the effect of blast damage on the strength of hard rock pillars using numerical models through a parametric study. The results indicate that blast damage has a significant impact on the strength of pillars with larger width-to-height (W/H) ratios. The blast damage causes softening of the rock at the pillar boundaries leading to the yielding of the pillars in brittle fashion beyond the blast damage zones. The models show that the decrease in pillar strength as a consequence of blasting is inversely correlated with increasing pillar height at a constant W/H ratio. Inclined pillars are less susceptible to blast damage, and the damage on the inclined sides has a greater impact on pillar strength than on the normal sides. A methodology to analyze the blast damage on hard rock pillars using FLAC3D is presented herein.
Highlights
The most common methods employed in hard rock mines are drilling and blasting
Assuming the blast damage on the pillars would decrease pillar strength, the results are presented in a normalized fashion, mainly for qualitative purposes, to understand the percentage decrease in pillar strength due to blasting when compared to the pillar strength with no damage effect
The decrease in pillar strength is considerable in pillars with W/H ratios evaluating pillar strength
Summary
The most common methods employed in hard rock mines are drilling and blasting. An inherent problem that exists with this method is the damage to the periphery of excavation induced by the blast. Some of the earliest research [1,2,3] stated over-break as the only major consequence of the blast damage. It was defined as the unwanted loosening, dislocation, and disturbance of the rock mass beyond the limits of the intended excavation design. Numerous studies have been undertaken to determine the extent of the blast damage on rock excavations [5,6,7,8,9]. Ouchterlony et al [10] have done field studies to determine the blast-damaged zone based on explosive type, charge concentration, and charge diameter. Distinction andblast blastdamage damage [4]
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