Pressurised gas has been ruled out as the cause of a
rockfall that killed two miners at the Austar underground coal mine last month.
By examining the gas monitoring system, investigators at the
Yancoal-owned mine have found that there was no evidence of higher gas readings
before or after the accident.
This means that the coal burst could not have been caused by
gas pressure as was surmised by some following the accident.
The workers involved were operating a bolter miner and shuttle
car, with bolting rigs on the miner.
Grant and Mitchell were on the left hand side of the bolter
miner when a burst from the coal rib caused a section of the rib, which was
supported with various lengths of bolts and mesh lost confinement and moved
into the roadway where the material engulfed the two men.
Five other workers involved with work at the time were
unharmed, and attempted to rescue the men, however the area was deemed
The Mine Safety Investigation unit report said that the
incident occurred 10 kilometres from the mine entrance and 555 metres
underground, where rib and roof strata of the coal seam is subject to
The investigation found that steel mesh held with chemical bolts
and cable bolts supported the roof and ribs of coal at the accident site, however
the extent and nature of the bolting is yet to be confirmed.
The investigation is presently examining the design of the
mine, geotechnical conditions and the suitability of engineering and strata
controls, as well as the systems of mining and safe work procedures in place at
Pictured is the site of the accident after the two bodies were recovered.