Outburst (mining) - Outburst Management

Outburst Management

Outburst management primarily focuses on the prevention of outbursts by pre-draining the gas from coal seams prior to mining. The aim of gas drainage is to lower the gas content of the seam below a certain threshold value, at which time it is considered safe to mine the seam. These threshold values should vary depending on the coal seam and being mined. Since the introduction of threshold values, not a single fatality due to an outburst has been recorded in Australia.

Gas drainage is achieved by drilling boreholes into the seam in advance of mining. Gas liberated from the seam into the boreholes is transported out of the mine via a pipe range.

Where standard gas drainage techniques are ineffectual, mine operators have a number of options. These may include:

• Remote mining - mining is carried out by remote control.
• Grunching - refers to the sequential drilling, blasting and loading out of the coal face, as opposed to the conventional mechanised method of mining.
• Induction shotfiring - using a charge (explosive) to test the face and induce an outburst if one is imminent. The explosion would have the effect of fracturing the face and relieving the stress on the face, transferring it deeper into the seam.
• Not mining that part of the seam - after all, lives are worth more than coal

Mining under "bomb squad" or outburst conditions is no longer considered acceptable, since this method still presents a fatal risk to at least one miner. "Bomb squad" refers to a special set of operating conditions that would be adopted when it was anticipated that an outburst could occur. Under "bomb squad" conditions, the following working methods would apply:

• Minimal manning at the face - particularly during the cutting of coal, only one man at a time was allowed at the face (the continuous miner driver)
• Armoured cabins were built on continuous mining machines - these cabins were thought to be able to protect the operator in the event of an outburst. This was subsequently proven to be wrong.
• Operators wore full-face masks, connected to a compressed air supply - once again, this was ineffectual in preventing fatalities from occurring.