3.2.4 Wall Support

All the openings in an underground mine are reinforced to keep them securely in place.

For example, to support the roof of the drifts, cable bolts several metres long are inserted into the rock and cemented along their entire length.

		Cable bolts in the roof of a mine drift.
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The cables are laid out in a grid, using a bolting machine. The bolting machine inserts the steel cable into the drill hole and injects the cement.

		Drilling holes for cable bolts using a Simba drill.
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To further strengthen the roof and walls, a steel grid is set against the rock and secured with cables or bolts.

		Setting the steel grid into place.
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If the underground openings are large and used frequently, the walls may be covered with sprayed concrete in order to provide additional support for the rock.

		Wall rock covered with sprayed concrete.
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A microseismic monitoring system, which detects small earthquakes in the mine, is used to monitor the stability of the walls.

If a drift is at risk of collapse, it is evacuated until the small earthquakes have become negligible again.

		Examples of microseisms.
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