Mining in Manitoba

 

Blasting Theory

 

Mining Systems

 

Historical

Explosives

Drill Patterns

Blasting Cycle

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1) Strength of the explosive should be proportional to the resistance of the rock.

2) The burden should be properly proportioned to the strength of the explosive and the resistance of the rock.

3) Blasting of the rock to leave 2 or more faces will require a smaller quantity of explosives than if only 1 free face is left by preceeding blast.

4) It is more economical to break to a system of regular faces and benches than to blast in an irregular manner

5) Where possible, the simultaneous firing of several shots grouped closely together often requires less powder than if shots are fired singly.

6) No more explosive should be used than is required to break rock to the proper size and leave it in the best position for handling.

In most mining operations, explosives are placed in drill holes. If explosives are placed in a drill hole and detonated, the result is usually a crater of varying size.

crater1.jpg (8499 bytes) The bottom of the cone is formed at the free face. If the rock is resistant to breaking, sometimes hardly any cone is formed. If the rock is easily broken, the cone may start at the bottom of the hole.
Wherever possible, 2 free faces are provided for an explosive. It is always best to have the hole filled with explosives parallel to one free face. freeface2.jpg (10282 bytes)
freeface.jpg (12133 bytes) A free face sometimes has broken rock lying next to it and this is called a burdened face. It has been found that explosives usually break well against a burdened face. The force of the explosive must compress it slightly so the solid rock can expand and break.

 

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