A pre-cast shaft system was developed for the mining industry as a result of the limitations to pile in overburden deeper than 30 m. A benefit of this pre-cast shaft system is that the overburden can be removed to a point where the raised-bore foundations can be piled.
The backfill is constructed to natural ground level in stages using these unique pre-cast shaft panels.
By using this method, 70 m of unstable overburden will not pose any problems to up-cast vent shafts or similar projects.
Greene Consulting Engineers (Pty) Ltd developed this new pre-cast shaft system in conjunction with Multikon. The first pre-cast systems to be constructed were three shafts at Bokoni Platinum Mine. The diameters of the shafts were 4.5 m, 4.8 m and 6.3 m respectively. With the rock level in the order of 50 m below natural ground level, it was especially beneficial to be able to remove 30 m of unstable overburden and to compact it back against the pre-cast shaft.
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