Mining in Manitoba
Cut & Fill Mining
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When sufficient information has been obtained from diamond drill core samples of a particular mining area, three main factors determine the feasibility of using mechanized cut and fill mining. They are :
- competency of the ground
- overall grade of ore
- length, width, and dip
The competency of the back and backs must be sufficient to allow workmen to safely work under the conditioned ground. As a general rule, 10 - 12' is left open to downbreak into on each successive cut, giving the stope an overall backheight of about 20'. The walls may be further controlled, where required, with additional sandfill. Areas where sand is poured tight to the back are called floodfilled.
Cut and fill mining is a fairly costly mining method as the back and walls nust be conditioned every cut to provide a safe working face. The overall lifetime grade of ore in the proposed stope must be sufficient to support this conditioning cost.
The length, width and dip of the orebody play a major role in the using cut and fill mining. Generally, cut and fill stopes are 600' - 1000' long, vary from a minimum width of ( 8 ' Mines Act ) to 35' and are particularly suited to areas where the dip varies or is shallow. Wher the ore exceeds safe width, pillars are left as support. ( These can later be retrieved, using Undercut & Fill mining.)
Layout
In the layout phase of employing cut and fill mining, four major items are considered for the a particular stope. These factors are :
- Sill Elevation
- Ventilation
- Ore Removal
- Services and Supplies
New stopes are silled out at base of rail of the level, and mined in 200 - 400 ' vertical slices. Generally the last 30 - 50 ' below the base of rail of the next level is left as a crown pillar.
Particular attention must be made to provide adequate ventilation to supply oxygen to breathe and to remove the diesel emissions and dust. Stopes are designed to have ventilation raises close to each end to provide through ventilation. Manways are the other major ventilation openings. Each stope has a ventilation manway at each end. A push/pull fan system provides air circulation.
Muck is removed from the cut and fill stope through footwall orepasses.
These footwall orepasses are designed to be outside the ore zone so that they will remain intact in the relatively strong footwall rock, as mining advances upwards.
Most raises are raise bored and culvert lined. A ladder, landings and a steelslide are installed inside the culvert to provide access for men and supplies from the level above. Air, water and sandfill lines provide services from the level above.
Additional manways are created for sandfill drainage and service manways which provide access for the L.H.D. equipment.