Mining in Manitoba

Stull Mining

Engineering Considerations

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This mining method depends on pillars for mass support and upon stoping spans which are largely self-supporting. Stulls are installed in a geometric pattern to carry working floors, to form the base for chute and manway linings, and to support local loose as may develop.

The method has been used on flat dips, but its widest application has been on steep dips where in narrow ore it competes with shrinkage stoping, perhaps most effectively in small orebodies and when wage rates are low. It does not require the broken reserve essential with shrinkage stoping, but compared with shrinkage stoping its greatest advantage is when widths are narrow enough to obstruct the free flow of shrinkage ore. This condition also involves the lowest unit cost for timber.

Through the stoping area the levels are carried on the crown pillars of stopes structure below and level intervals in continuous ore will vary from 100 to 150 feet.

The pillar structure must be based on a percentage of support which will ensure stability of the area as a whole. If the spans between crown pillars are excessive for the ground the horizontal span may be shortened by introducing rib pillars.

Occasionally in the final pulling of very narrow shrinkage stopes, as the ore is drawn down the placing of stulls follows in an effort to hold the walls in place and minimize dilution. This represents a compromise with stull stoping prior to a change of method usually from shrinkage to some form of cut-and-fill.