Block-splitting using black powder
First, a groove (along which the rock will be split) is made, following the rock's cleavage (direction of cracks).
Next, blasting holes are made along the groove, either using the hammer action of a rock drill (fitted with a chisel end) or a crowbar if the rock is soft (sandstone or limestone).
Average productivity rate in sandstone: 1.5 work-days per linear metre.
Boring in soft rock
In hand drilling soft rock such as sandstone, water is used to free the hole of rock dust and thereby facilitate boring.
The number of holes depends on the size of the rock mass to be split Next explosive cartridges are placed at the bottom of the holes. The number of cartridges per hole is determined by the strength required of the explosion, which in turn also depends on the size of the block to be split.
Black powder is primed using a slow fuse which transmits a flame at the rate of 1 metre in 90 seconds. Once the primed cartridges are in place in the holes, the holes are packed with clay or sand.
The fuse is lit by the certified blasting officer only after all quarry workers have been guided to a safe location.
The shock wave caused by the explosion will be guided by the groove.
Use of explosives is dangerous. This means that safety precautions must be taken.
All stipulations contained in national legislation and regulations, as well as recognised guidelines on the use of explosives, must be respected. Rules regarding the transport, storage and use of explosives and detonators aim at protecting people and property against bodily or material harm. Only holders of blasting certificates can be authorised to handle and use explosives.
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