Pre Blasting and post Blasting inspection for data collection and blast design is very important so as to performance a profitable and productive Blasting.
Some of the pre-blasting inspection carried out before Blasting includes;
1. Ground water condition (in-hole water check)
2. Rock face discontinuity mapping
3. Drilling parameters collection.
4. Free face checking.
1. Ground water condition (in hole water)
Water may be present in the mine either through surface inflow or underground water outflow.
Ground water condition affects Blasting materials, expecially when using a non water resistant Explosive like ANFO. This may result into MISFIRE and poor fragmentation.
All holes must be inspected and those with water should be noted.
Water tend to reduce the sensitivity of non water resistant Explosive. Explosive like Dynogel and emulsion gel and other water resistant Explosive should be use in noted water filled holes.
Hole with water can also be drained or flush by high pressurized air before charging.
2. Discontinuity mapping
Mostly in mine face and floor fractures occur due to overbreak induced by the previous Blasting. Some cracks in rock may be of wide aparture capable of stealing grain Blasting Agents and concentrating it at a point ( this may result into formation of flyrocks if the concentrated/trapped Explosive is close to the free face where burden is less).
Thou fractures may tend to appear in rock due to natural phenomenon like weathering and stress relief. The discontinuity condition of rock mass need to be checked before drilling and possibly after drilling to contain it effect on Blasting.
3. About drilling parameters, this is very important as poor drilling design will totally affect Blasting. Some of this design parameters are burden and spacing, hole Depth and hole diameter.
Imperfect hole parameters affect not only burden movement during Blasting but also affect Blasting cost, environmental safety and Blasting result.
Poor hole burden distribution affects burden movement during Blasting which tends to create the production of unwanted Blasting result. The concept of Achieving good Blasting, we need to ensure our drilling design is properly done and if possible checked on softwares like O-pit blast for outlier drill holes.
Most mining companies complain of blast overbreak and poor fragmentation. The damage created by Blasting shock waves can be contained by proper drilling design which help to optimumly ultilize Explosive energies during detonation.
Checking Bench or mine free face provided by the drilling team is also an important thing to consider during Blasting. This will help to control charge density rate at the first hole row to prevent the possibility of flyrock and other Blasting created hazard.
Some of the post-blasting inspection includes; Misfire checking, wall and roof scaling, Blasting fume and gas testing, fragmentation checking and analysis.
Get the complete detailed post-blast explanation later.
Thanks.
GIANT MINER.
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