MINING METHODS

In keeping with Sigra's background of innovation it has been involved in designing several new mining systems.

One application involved a need to mine a comparatively narrow, near vertical orebody daylighting in the side of a mountain with a boulder field above. The limited size of the orebody and the difficulty in dealing with the boulder field eliminated the option of an open cut. Funding restraints meant that ore was needed immediately and the delay and costs of developing a conventional underground mine were prohibitive. In addition it was highly undesirable to have to truck large quantities of rock back up the mountain from the processing plant for a fill stope system.

The solution proposed is a combination of mining and civil engineering expertise. It involves mining a shallow slot over the orebody and casting a thick reinforced concrete slab in the slot. Mining proceeds below the slab along the orebody using holes in the slab above for fan ventilation. Once the new roadway is mined a new floor slab is cast and then mining proceeds below the slab. The system will produce ore quickly with minimal development and with minor environmental damage to the mountain. The system is shown schematically in drawing D8.

Another design uses a chain based mechanical cutting system for coal with water being used to sluice the coal to a gathering point.

When the Addington highwall mining system was in fashion in the early 1990s roof failures frequently trapped the conveyor cars. To overcome this Sigra invented a rolling roof support system based on a conveyor supported on pneumatic struts. This is shown in drawing D9.

Sigra's longwall recovery road support system is shown in drawing D3