Boring and mining

Published on 8 February 2008
Boring machine (Photo DTP Terrassement)

In rocky terrain the rocks have to be broken to be able to extract them from the ground and load them into the transport equipment.
To be able to insert explosives into the rock, holes have to be bored.
Hole diameter and length, as well as the spacing between the rows of holes and the intervals between holes in any given row depend on a number of parameters:

• Rock type: massive granite, basalt, limestone...

• Presence of water in the holes

• Type of explosive: ammonium nitrate fuel oil, gelatin
dynamite, gel and emulsion explosives...

• Detonator type: electric, electronic, non-electric...

• Desired block size: large riprap, materials for crushing...

• Desired shape of cutting

• Quantity of materials to be mined (1,000 m3, 100,000 m3, 1,000,000 m3, in excess of one million m3)

• Presence of residential housing, roads and sensitive structures that must be retained in their original state (bridges, electric power lines, natural gas pipelines, railway tracks...)

From amongst all this information the engineer responsible for the mining on site must choose one mining method. He will do this:

• Based on his experience, that of his company and that of specialist consultants

• After trial blasting, followed by further trial blasting as required

• By recording the vibrations and noise...

• By adapting the blasting schedule to the exact conditions as the site evolves

Computer modelling is increasingly advanced, but trials are needed to best determine the parameters of the equations involved.