Three men are trapped bellow ground following a collapse at an unlicensed coal mine in Paschim Bardhaman District in West Bengal on Sunday 13 October 2019. Four men were underground in the mine, in the village of Aldhi, when the collapse occurred. The fourth man was able to escape and raise the alarm, but rescue attempts by local police and a specialist team from Eastern Coalfield Limited have been thwarted by poisonous methane gas within the mine, making it unlikely there will be any further survivors.
The approximate location of the 13 October Aldhi mine collapse. Google Maps.
Coal is formed when buried organic material, principally wood, in heated
and pressurised, forcing off hydrogen and oxygen (i.e. water) and
leaving more-or-less pure carbon. Methane is formed by the decay of
organic material within the coal. There is typically little pore-space
within coal, but the methane can be trapped in a liquid form under
pressure. Some countries have started to extract this gas as a fuel in
its own right. When this pressure is released suddenly, as by mining
activity, then the methane turns back to a gas, expanding rapidly
causing, an explosion. This is a bit like the pressure being released on
a carbonated drink; the term 'explosion' does not necessarily imply
fire in this context, although as methane is flammable this is quite
likely.
Fire is much feared in coal mines due to this combination of
flammable gas and solids, with methane and coal dust both potentially
explosive when they come into contact with naked flames. To make matters
worse, the limited oxygen supply in mines often means that such fires
will involve incomplete combustion, in which all the oxygen is used up,
but instead of forming carbon dioxide forms the much more deadly carbon
dioxide, with potentially lethal consequences for anyone in the mine.
Coal is also comprised more or less of pure carbon, and therefore reacts
freely with oxygen (particularly when in dust form), to create carbon
dioxide and (more-deadly) carbon monoxide, while at the same time
depleting the supply of oxygen. This means that subterranean coal mines
need good ventilation systems, and that fatalities can occur if these
break down.
The mine is of a type known locally as a 'rat hole', due to the small
nature of the entrance holes, in which miners dig into the side of a
hill using hand tools, until they reach a seam of valuable minerals,
usually coal, but limestone, kaolin, clay, granite, glass sand, and
uranium ore are also sometimes excavated in this way. Despite the best efforts local authorities, such mines thrive across the Ranigunj-Asansol Coal Belt of West Bengal, where a lack of economic prospects creates a ready supply of cheap labour. Many such mines are controlled by organised criminal groups, and tend to be well hidden to disguise them from both the authorities and rival gangs.
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