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Drilling and blasting are increasingly seen as a single tailored activity.
accuracy: the fragmentation is uniform.“ It also controls the ground vibrations. We have a lot of communities around the quarries, so you want to control the mass per delay( kilograms of explosives all firing at the same time, which control ground vibration air blast) without creating inefficiency in bringing down a bench. You still want to fire your big benches from a productivity point of view, so what you do effectively is divide your blast into two, so you put a detonator in the top half and a detonator in the bottom half, fire the top half and then fire the bottom half. To all intents it’ s a single blast, but in reality, you’ re able to control the mass per delay.”
What automation means for a quarry is that you can now have an automated drill rig next to the high wall— this addresses the risk of things falling off the face and landing on people, so you’ re removing people out of the danger zone.
A major factor in blasting— whether surface or underground— is the reef size, which affects the hole size. In the underground environment, it is approximately 23kg to 42kg per hole; in civils, it is 42 to 89; in a quarry, it is 89 to 127; and above 127 in large-scale mining and up to 311kg per hole in coal mining. In opencast mining, you can get up to one and a half tons per hole. Tose has a specialised team that monitors such holes— size and location— and how the explosive is likely to perform in that hole, looking at how the rock is actually breaking.
This has equal applicability in quarrying, and in China they are looking at not blasting an entire bench but cutting it to the exact size, and having it fall directly onto a conveyor that takes it to a crushing plant— but there’ s a substantial capital cost to that type of equipment. But once you’ ve got over the capital cost, the cost of a conveyor is about a third of transporting it by road.
“ This means the job of a geologist is changing, as the drilling rigs are able to determine what is happening below ground and your ground plan suddenly becomes a thousand times more accurate.
“ A blaster is now able to successfully initiate a blast up to 2km away from the actual event, offering much safer operating conditions. The pre- and post-blast capability of the system enables a user to prevent a misfire from occurring, or to at
20 _ QUARRY SA | SEPTEMBER / OCTOBER 2018