Bord-and-pillar mining explained

Shear size: A longwall miner in action on the coal face underground.
Shear size: A longwall miner in action on the coal face underground.

What is bord-and-pillar mining?

Two main methods of extraction are used for underground coal mines in New South Wales: longwall and bord-and-pillar extraction.

Bord-and-pillar extraction is the older of the methods, and 

The word “bord” is not a misspelling of “board”, but a mining term for an underground space or room created to access the coal deposit. It originally meant a face of coal parallel to the natural fissures.

Pillars of coal are left behind to support the roof as the coal is cut away with a machine called a continuous miner.

Bord-and-pillar mining is used in first workings of a deposit, and when irregularly shaped deposits, or sensitive environmental conditions, call for a lighter touch.

This method is used at Wongawilli after the longwall miner was buried in a roof collapse.

Longwall mining is newer, and revolutionised coal mining. It involves giant and super-expensive machines called longwall miners shearing away a “wall” of coal at a time.

As the miner moves on, hydraulic supports are removed and the roof collapses into the void left behind – an area known as the “goaf”.

Cutting coal: Using a continuous miner at the Dendrobium colliery at Mt Kembla in 2008.

Cutting coal: Using a continuous miner at the Dendrobium colliery at Mt Kembla in 2008.

Longwall mining extracts more coal as the pillars are not left behind. But the price is that it causes significant subsidence, with the ground above potentially cracking and sinking.

This is used in South32’s Illawarra mines, and was used at Russell Vale while the previous approval was valid.