Sigra’s staff are well versed in the usual coal mining techniques of
- Bord and pillar development
- Wongawilli extraction
- Longwall extraction
In addition it has innovated to produce alternative mine designs. One of these is the sluiced hydraulic longwall mining system. This was designed for moderately sloping seams (10 to 35o) which have a hard roof and floor.
It involves developing gate roads which may be some hundreds of metres apart on a slope, and directionally drilling between them on a steeper slope. The directional drilling bottom hole assembly is then removed and replaced with a sluicing head to wash the coal away so that it flows down the enlarged hole, which may be several hundred metres long, into the lower gate road and from there to a sump from which is conveyed to surface.
The drilling and sluicing process may then be repeated to form a longwall face with a caved zone behind. The system has the potential to deliver a longwall mine for a very low capital investment. It also has the ability enable a series of thin seams to be mined that would otherwise not be economic.
Other designs that Sigra has invented are rolling roof supports and ventilation systems for highwall mining.
In the metalliferous area Sigra staff have worked in the fields of:
- long hole open stope mining
- narrow vein mining
- block caving