Abstract:
In 2015, after amendments to the explosives regulations, stemming became a mandatory activity for all
South African mining operations. There are, however, circumstances in which it is thought stemming
has an adverse impact on the blasting outcome. Some of these circumstances include blasting in
hot holes, in reactive ground, or when blasting a pre-split. In order to determine when stemming is
necessary, its role in the control of adverse blasting phenomena and impact on explosive performance
were reviewed. Stemming was found to play a significant role in the fragmentation process and burden
movement. Additionally, stemming significantly influences the control of flyrock, air-blast, and toxic
fume generation. The review of the literature indicates some motivation for not using stemming for presplit,
trim, hot hole, and reactive ground blasting, provided the benefits associated with not stemming
the holes outweigh the risks of stemming them. Best practice for stemming from the literature indicates
a stemming length of 0.7 × burden is best for larger hole diameters, and 20 to 30 × Ø for smaller hole
diameters. Crushed aggregate appears to be the most effective stemming material. The South African
explosives regulations pertaining to stemming were found to be consistent with those of Australia and
the USA.
