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Sublevel Stoping

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Mining Processes

Sublevel stoping is a method of underground mining method that involves vertical mining in a large, open stope that has been created inside an ore vein. Usually the stope operates as the center for production. In sublevel stoping, this is not the case. The stope is not meant to be occupied. Drilling, blasting, and mining are carried out at different elevations in the ore block. Sublevel stoping has been used in a number of Canadian operations from mining nickel in Manitoba, to gold in Ontario, to lead and zinc in the Northwest Territories.[1]

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[edit] Process

In sublevel stoping, an ore pass is first drilled into a series of sublevel drifts that begin at a lower elevation within the stope, ending at a higher one. The drilled sublevels are situated directly above a main haulage level. Jumbo drills are used to selectively drill out holes in the roof of the drifts; the holes are then filled with explosives. The explosives, once detonated, blast apart the roof of the sublevel drift and loose rock and muck fall through the drilled ore pass. Load haul dump trucks (LHDs) and scoop trams are used to transport the muck to another ore pass where it is placed into a crusher before being elevated up to the surface on a conveyor. Blasting of the drift roof continues until it is out of reach of the drilling jumbo. Another jumbo drill working on another higher drift is used to intersect the stope with drilling and blasting. The loose and broken ore falls down to the lower sublevel drift. A load haul dump truck or scoop tram, able to maneuver inside the lower drift, loads up the ore and muck and dumps it into the ore pass. The excavation process is repeated until the stope is left completely empty and then backfilled from the bottom up to support the stope walls and roof. The backfill materials used are made of one or any combination of sand, rocks, waste rock, cement, or dewatered mill tailings.[2]

[edit] Swag!

There are three different variations of sublevel stoping used in underground mining operations.

[edit] Blasthole Method

This method involves creating a vertical slot at an open end of the stope. Miners drill a radial pattern of drill holes in the sublevels of the stope. The drill holes are then loaded with explosives with blocks of ore get into the open stope.

[edit] Open-ended Method

Similar to the blasthole method, a slot must be created at an open end of the stope. Parallel holes are then drilled from the top to the bottom of the stope from a sublevel as wide as the stope, located near the top. Vertical slices of ore are then filled with explosives and blasted into an open part of the stope. The advantage of this method is it permits the drilling of larger holes and more efficient use of explosives.

[edit] Vertical Crater Retreat

The vertical crater retreat is a method of sublevel stoping patented by a Canadian explosive firm. The drill pattern used is similar to the open-ended method, except the ore is blasted in horizontal slices.[3]

[edit] Equipment Used

[edit] References

  1. Hartman, L. Howard and Mutmansky, M. Jan. Introductory Mining Engineering. John Wiley and Sons, 2002. 344
  2. Sublevel Stoping. BC Minerals. 2008-10-07.
  3. Hartman, L. Howard and Mutmansky, M. Jan. Introductory Mining Engineering. John Wiley and Sons, 2002. 344.